Showing papers in "Journal of Eukaryotic Microbiology in 1954"

The Relation of Autoǵamy to Senescence and Rejuvenescence in Paramecium aurelia

Abstract: Two problems were posed for experimental analysis: (1) What is the effect of omission of both conjugation and autogamy on fission rate and other characteristics of P. aurelia? (2) What effects does autogamy have when it occurs after intervals of varying length since the last previous fertilization? These questions were explored most thoroughly in stock R of variety 1 and stock W of variety 2; but some data are also presented for stocks S and 60 of variety 1, stock E of variety 2, and stocks 29, 32, 47, and 51 of variety 4 and their hybrids. In essential features the results on all stocks and varieties are in agreement, as far as they go; but the details differ. To the first question, the answer is simple and clear: under the conditions of culture employed, fission rate declines and death eventually occurs in daily isolation lines that omit both conjugation and autogamy. The maximum number of fissions until death was about 350 in stock R (variety 1), about 300 in stock W (variety 2) and perhaps as low as 200 in variety 4. Early in life the fission rate is high and shows little or no decrease for a considerable time; it then decreases progressively and slowly for a long time; and may finally decline at a faster rate. Decline and death are preventable by permitting autogamy to occur repeatedly without unduly long intervals between them. Viable lines maintaining high fission rate may be continued in this way without apparent limit. The answer to the second question is more complex, for autogamy may have any one of several consequences. Even in controls undergoing recurrent autogamy at relatively short intervals, autogamy sometimes yields nonviable clones or clones with low fission rate; but it usually yields viable clones manifesting normal high fission rate. Likewise, the most vigorous clones arising at autogamy from parents that have not begun to decline in fission rate show no increase in fission rate, but undergo a whole life cycle consisting of as many fissions as the total life cycle of the parent from its origin at fertilization until its death. As the parents progressively decline in fission rate, the most vigorous clones to which they give rise at autogamy again initiate new life cycles characterized at the start by normal high fission rate. Since the latter is above the fission rate level of the parent, rejuvenescence is at once apparent. However, not all autogamous offspring of aging parents initiate new life cycles at the normal maximum fission rate level. Some exhibit an immediate marked decrease in fission rate below the level of the controls and the parents and may maintain about the same fission rate for long periods. Others drop at once to low fission rate and appear to start to decline further very soon. Still others show very little or no change from the level of the parental fission rate, even when the latter has declined greatly at the time of their origin. Variation in the fission rate of offspring arising at autogamy is one of the capital facts brought out by this study. Rejuvenescence at autogamy occurs, but only in some autogamous offspring. At the other extreme, autogamy in aging clones—as in controls—sometimes leads to death at once or within several fissions. The frequency with which this happens increases markedly with the age of the parent and eventually it becomes impossible to obtain viable autogamous offspring, as also reported by other investigators. At this stage in the life history, the doom of the strain is sealed: it will die eventually without autogamy and it will die quickly if it undergoes autogamy. Finally, in the last stage of the life cycle, autogamy can be induced only with difficulty and in a small proportion of the animals, if at all. Yet, in spite of all the risks involved, the animals must undergo autogamy (or conjugation) or perish. Of those that take the risk, if they have not waited too long to do so, some will survive and be rejuvenated. The end result of our study is thus to place on a firm experimental basis the conclusion to which Woodruff and Erdmann (47) were forced forty years ago by the logic of the situation, even in the absence of experimental analysis: conjugation is not essential for P. aurelia; autogamy (endomixis) alone can maintain the organisms in life and vigor. The main hypotheses that have been advanced to account for senescence and rejuvenescence in ciliates are discussed in the light of the foregoing results and other available knowledge. It is concluded that present information does not yet permit a decision as to the correct interpretation. Certain values and difficulties of the various hypotheses are pointed out, as are some opportunities to bring recent advances in knowledge to bear decisively on a choice among them. It appears possible that the ultimate solution of these problems will involve elements of more than one of the current hypotheses.

The Use of Tetrahymena to Evaluate the Effects of Gamma Radiation on Essential Nutrilites

Abstract: The complete synthetic medium for the growth of Tetrahymena pyriformis E was subjected to gamma-radiation from cobalt60 A dose-response curve indicated the range of radiation which damaged the medium so that growth of Tetrahymena was inhibited The essential vitamins and amino acids which comprise the medium were individually irradiated in solution Media were prepared with single irradiated components and tested for their ability to support growth of the protozoa Thiamine, riboflavin, pantothenate, pyridoxine, folic acid, and thioctic acid were destroyed by less than 1 × 106 rep, while 2 × 106 rep was required to inactivate nicotinic acid Most amino acids proved to be relatively radiation-resistant At the high radiation levels of 1 × 107 rep and 23 × 107 rep respectively, only serine and methionine were damaged All other amino acids remained biologically active even after receiving 23 × 107 rep, the highest level of radiation employed Organoleptic observations, however, showed radiation-caused color and odor changes in many of those amino acids whose biological activity for Tetrahymena was unaffected The nucleotide, guanylic acid, was also inactivated at 23 × 107 rep

Studies in carotenogenesis Some observations on carotenoid synthesis in two varieties of Euglena gracilis

Abstract: Euglena gracilis v. bacillaris and E. gracilis v. fuscopunctata produce the same three carotenoids, β-carotene, lutein and neoxanthin in approximately the same relative amounts. Lutein is the major pigment and β-carotene represents about 10–15% of the total. The concentration of carotenoids in E. gracilis v. bacillaris is very high, reaching 700 mg./100 g. dry weight. Streptomycin (0.02%, w/v) and darkness reduced growth of E. gracilis v. bacillaris by about 50% and carotenoid synthesis by about twenty times. Diphenylamine (1/70,000) reduced growth and carotenoid synthesis equally (about 50%). In no case was the synthesis of more saturated polyenes (the phytofluene series) stimulated. The nature of the eye spot pigment is discussed.

The Literature on Tetrahymena: Its History, Growth, and Recent Trends

Abstract: The literature involving the genus Tetrahymena has become so voluminous in recent years that some consolidation of it appears advisable. Through 1953 well over 500 papers, scattered through more than 100 scientific journals, have been devoted in whole or in part to studies in which species and strains of this genus, under a variety of names, have been employed as one of the experimental animals. Nearly half of these works are cited directly in the present paper. The major areas of research in which these ciliates have been used to advantage include physiology and biochemistry, containing nearly 60% of all the papers, cytology and taxonomy, and three smaller fields arbitrarily designated as cytogenetics, morphogenesis, and parasitism. Tetrahymena's sustained popularity as an object of research may be considered as due primarily to its ability to thrive axenically in a chemically defined nutrient medium and secondarily to such factors as its ubiquity in nature, its ready adaptability to a variety of ecological situations (including endoparasitism), its possession of a relatively primitive and fundamental type of buccal ciliature of considerable phylogenetic significance, and its exhibition of the sexual phenomena of conjugation and autogamy.

Anomalies in Regeneration of Paramecium

Abstract: Using two different stocks of P. caudatum and four of P. multimicronucleatum it was observed (total of 25 cases) that starved fragments do not regenerate either end of the cell up to the time of death though they survived long past the time required by feeding fragments to regenerate. Fragments which were prevented from regenerating by an initial period of starvation later regenerated when supplied with nourishment (69 cases). Only three fragments failed to recover normal form when fed, two showing conspicuous abnormality instead and one remaining unable to feed. Short anterior fragments (32 cases) and posterior fragments (four cases) which are nucleate but do not include the feeding organelles can neither feed nor regenerate either normal body shape or the oral structures. In seven cases it was found that when the oral region of whole animals was injured they could no longer feed and in six of these cases no mouth or gullet could be found. It is therefore suggested that organelles of ingestion cannot be regenerated when excised or damaged even though the normal site be present. These observations are considered to demonstrate that regeneration in Paramecium is entirely different in type from that of most protozoa in that it occurs only through feeding and subsequent growth if ingestive organs are already present in part at least. It does not occur by the remodeling of body shape, with the formation of oral primordia derived from more general cytoplasmic differentiations, as is the case in most ciliates. The original surprise of Balbiani in finding that his fragments of Paramecium did not regenerate like other ciliates is now explained.

Coenzyme A and the Malaria Parasite Plasmodium lophurae

Abstract: The extracellular development of Plasmodium lophurae in vitro was favored by the addition, to the erythrocyte-extract medium, of a coenzyme A (CoA) preparation of about 75% purity. The effect of CoA was the same regardless of the concentration of free pantothenate in the medium, indicating that the parasites require the complete coenzyme rather than its pantothenic acid moiety. Erythrocyte extracts were found to contain enzymes which hydrolyzed added CoA at a rate such that 8 units per ml. of coenzyme was only slightly destroyed after 3 hours’incubation but almost completely destroyed after 18 hours’incubation at 40°C. The CoA content of erythrocytes from chickens or ducks heavily infected with P. lophurae was about twice as high as that of erythrocytes from uninfected birds. The increased CoA was associated with the parasites, an observation suggesting that malaria parasites can accumulate this essential growth factor which they cannot synthesize. The CoA concentration in the livers of infected chickens was approximately 40% lower than that in the livers of control chickens. The livers of ducks on the 6th day of infection had a slightly lower CoA concentration than those of uninfected ducks. This depletion in CoA, together with the depletion in biotin previously demonstrated in P. lophurae infection, may play a role in the pathology of this infection.

The Ecology, Life History and Parasitism of Tetrahymena [Paraglaucoma] rostrata (Kahl) Corliss

Abstract: Tetrahymena [Paraglaucoma] rostrata (Kahl, 1926) Corliss, 1952 occurs commonly in litter and occasionally in soil. It has previously been recorded from moss. In nature it feeds on cytolyzed or moribund tissue, but feeds on bacteria and flagellates in the presence of peptone. It is a facultative parasite of enchytraeid worms which it infects through degenerate setal follicles. It may also infect accidentally injured worms. The ciliates are attracted by histolysis and by peptone. Resistant cysts are formed regularly in the absence of food and encystment appears to be accelerated by crowding. Excystment is readily obtained with hypotonic salt solution. Theront, trophont, tomont and tomite stages are recognizable in the life cycle. Conjugation has never been observed.

The Oxidative Metabolism of a Cryptomonad Flagellate, Chilomonas paramecium*

Abstract: Tests based on respirometric and population growth methods for the analysis of oxidizable substrates for Chilomonas paramecium revealed that only those substances tested which are intermediates in terminal cyclic respiratory mechanisms (pyruvate, lactate, acetate, α-ketoglutarate, succinate, fumarate, L-malate, oxalacetate, but not citrate, cis-aconitate or DL-isocitrate) were attacked. These organic acids, and the fatty acids and alcohols earlier known to be used, n-butyric, n-caproic and n-caprylic acids, ethyl, n-butyl and n-hexyl alcohols, were the only carbon compounds oxidized by C. paramecium under the test conditions employed. Utilization of acid substrates was found to be pH-dependent. Reproductive and respiratory rates were related to the pKa values of the compounds. Oxidation of acetate, lactate, and pyruvate, however, was observed at pH values where their molecular form was present in exceedingly small amounts. Naturally-occurring α-amino acids, amines, glycolysis intermediates (3-phosphoglyceric acid, glucose-1-phosphate, hexose diphosphate) and degraded intermediates of glycolysis (glyceric acid, glycerol, dihydroxyacetone, glucose), two-carbon compounds more oxidized than acetic acid (oxalic, glycolic, glyoxylic acids, glyoxal, ethylene glycol), and formic, tartaric, malonic, and glutaric acids, were not used. Respiration in the presence of single members of the group of oxidizable substrates was sensitive to malonate and fluoroacetate. Malonate inhibition of succinate oxidation could be reversed by an increase in succinate concentration, but the relationship was not competitive; possibly because of permeability differences between the substrate and inhibitor. Fluoroacetate inhibition was accompanied by the accumulation of citric acid. The experiments on substrate oxidation, and the effects of inhibitors on the respiratory metabolism of the flagellate, are considered to provide evidence for the operation of the Krebs tricarboxylic acid cycle as a terminal respiratory mechanism in C. paramecium.

Trichodina myicola n. sp., a Peritrichous Ciliate from the Marine Bivalve Mya arenaria L.

Abstract: A new ciliate from the marine clam Mya arenaria is described and figured. The form is designated Trichodina myicola with specific characters as follows: Bell-shaped to discoidal; length 31–86 microns; diam. 62–103 microns; diam. denticulate ring 29–46 microns; 26–36 denticles; diam. of basal disk 42–79 microns; adoral ciliary spiral performs slightly more than one turn; posterior ciliature in three closely applied, concentric tiers: an anterior circlet of marginal cilia, a middle circlet of overlapping membranelles, and a posterior circlet of inner cilia; macronucleus C-shaped; micronucleus small, round, lying near outer curvature of left arm of macronucleus; large contractile vacuole present near end of left arm of macronucleus. Taxonomy in the genus Trichodina is discussed and outlined. Special attention is given to details of the oral ciliature. T. myicola is compared with other members of the genus. A checklist of Trichodina species is presented.

Reorganisation du Type Endomixique chez les Loxodidae et chez les Centrophorella

Abstract: New investigations of the nuclear cycle in the gymnostome ciliate Loxodes rostrum verify the long-neglected hypothesis proposed by Butschli that in this multinucleated ciliate the macronuclei never divide. The consequences of this “caryosterose” are compensated for by a process of endomixis, that is, by the transformation of a certain number of the micronuclei, during vegetative multiplication, into new macronuclei. The nuclear cycle in the gymnostome Centrophorella fistulosa does not show any aspect of nuclear division. Interpretation of this supposes the existence of polyenergid nuclei which fragment, during the interdivisional period, into subnuclei; among these some evolve in the somatic and macronuclear direction, before disappearance by karyolysis; others, corresponding to the micronuclei, grow by endomitosis, and reconstitute the polyploid and polyenergid nuclei. Thus the very particular nuclear cycle of C. fistulosa is believed to exhibit a new aspect in the endomictic process of nuclear reorganization.

Transfaunation Studies on the Host Specificity of the Enteric Protozoa of Rodents

Abstract: Breeding colonies of protozoa-free laboratory rats (Rattus norvegicus) and golden hamsters (Mesocricetus auratus) were established by early weaning or by drug treatment. Attempts were made to transfaunate the enteric protozoa of various rodents to protozoa-free progeny of these colonies. Efforts to transfer the fauna of guinea pigs (Cavia porcellus) to rats and hamsters have failed and indicate that this fauna is physiologically isolated as well as morphologically distinct from that of other laboratory rodents. The faunas of rats and hamsters appear to be morphologically identical and freely interchangeable. That certain of the species found in rats and hamsters also occur in the mouse (Mus musculus) is indicated by successful transfaunations: mouse to rat and hamster. The suggestion is made that the fauna of the mouse and rat is indigenous but that the fauna of laboratory hamsters may have been acquired since domestication. Hexamastix muris from Neotoma fuscipes and Trichomonas microti from Microtus pennsylvanicus have been transfaunated to rats. Other enteric protozoa from these hosts and also from Marmota monax and Dipodomys merriami have not established themselves in rats and, if morphological differences cannot be found, should be considered biological races of their counterparts in the fauna of laboratory rodents. Species of lumen-dwelling enteric protozoa should be based upon morphological distinctions and not upon host specificity. The latter, as demonstrated by these experiments, is not rigidly determined.

The Diatom Flora of Bethany Boǵ

Abstract: The results of these studies indicate that the first diatom flora developed at the 13-meter level. The flora at 12 meters increased. At the 11- and 9-meter levels the lake became increasingly eutrophic. Both plankton and benthic forms were present. At the 8- and 7-meter levels the lake was in a transitional stage from lake to bog conditions. From 6 meters to the surface bog conditions were present.

Autogamy in Paramecium polycaryum

Abstract: Mass cultures of a stock of Paramecium polycaryum maintained over a period of several years showed abundant and frequent nuclear reorganization stages resembling those of ex-conjugant and ex-autogamous animals of other species of Paramecium. Conjugation has never been reported for P. polycaryum, nor has it been found in these studies. Cytological examination of stained preparations revealed a process of autogamy in P. polycaryum, closely similar to that described previously for P. aurelia. As a rule, all four of the micronuclei, the typical vegetative number in P. polycaryum, engage in the first prezygotic division which is characterized by the formation of prophase crescents. Variable numbers of the eight nuclei continue with the second division. A maximum of sixteen nuclei may result. Apparently, only one of these normally completes the third prezygotic division to form the gametic nuclei, although more than one may initiate it. A fusion nucleus (synkaryon) arises in, or near, a paroral cone, thus paralleling autogamy in P. aurelia. A series of postzygotic divisions produces eight definitive nuclei, four of which become macronuclear anlagen and four remain micronuclei. The first division of the synkaryon results, possibly, in the formation of a viable nucleus and a non-viable one, as in ex-conjugants of P. caudatum. After the last micronuclear division, a skein evolves from the old macronucleus which has become flattened and leaf-like. The skein rapidly segments into “sausages” which transform into spherical fragments, about thirty in number. Two cell divisions restore the normal vegetative nuclear complex.

Enzyme Systems in Tetrahymena pyriformis S. VI. Urea Formation and Breakdown

Abstract: Cell-free extracts of Tetrahymena pyriformis S synthesize citrulline from ornithine, and arginine from citrulline The extracts also show arginase activity Urease activity at various pH values has maxima at both pH 56 and 74 This points to two distinct enzymes The presence of urea in ciliate cultures during early stages of growth, and its absence during the stationary phase of cultures, correlate with the shift in pH of the culture media and with the activity of the “alkaline” urease at various pH values

Plagiopyla minuta and Euplotes balteatus, Giliates of the Sea Urchin Strongylocentrotus dröbachiensis

Abstract: Of 165 sea urchins (Strongylocentrotus drobachiensis) examined in the Mt. Desert Island region, 41 harbored the intestinal ciliate Plagiopyla minuta in considerable numbers. Division in this ciliate is clean; i.e. it is not accompanied by the visible elimination of macronuclear material. Long periods (probably several weeks) of vegetative life appear to alternate with brief periods of intense divisional activity in P. minuta. Twenty-five of these same urchins also contained in their digestive tracts a species of Euplotes which was identified as E. balteatus. This hypotrich was also found commonly in the region as a free-living organism. Dividing specimens were found regularly in the urchin, and such specimens showed the usual macronuclear reorganization which occurs in Euplotes and its near relatives. The evidence indicates that E. balteatus is a facultative commensal, which is perhaps now in the process of acquiring the endozoic habit.

Discotricha papillifera, n.g., n.sp. Cilié psammobie de la Famille des Trichopelmidae

Abstract: A new sand-dwelling ciliate, Discotricha papillifera n.g., n.sp., is described and allocated to the trichostome family Trichopelmidae. The species seems to be one of the most highly differentiated members of the family. The peculiar type of its body ciliature and of its buccal structures suggests affinities with certain other major groups of ciliated protozoa; from an evolutionary point of view the organism appears to show close relationship to the gymnostome family Chlamydodontidae.

Origin and Morphogenetic Movements of the Pores of the Contractile Vacuoles in Paramecium qurelia

Abstract: The position of the contractile vacuoles in non-dividing Paramecium aurelia, as judged by that of the pores, is relatively constant both laterally and longitudinally, as is the distance between them. Some variability of the distance between the pores persists from the recent fission among the smaller animals of normal shape. At the onset of fission two new vacuoles appear, one anterior to each of the old vacuoles; all the vacuoles must undergo relocation because their mean positions now are somewhat removed from that in the non-dividing animals. The pores of the front daughter are too close together: the anterior pore is too far back, and the posterior is too far forward; likewise the pores of the hind daughter are too close together: the anterior too far forward as well as the posterior. The relocation does not begin until shortly before separation of the daughters and is practically complete by the time the daughters have assumed their normal length/width ratio after separation. A neuroneme connects the pore to one of the basal granules adjacent to its place of origin, now far removed. Occasionally more than one new pore appears at the usual time and place during very early fission; these are very close together and usually serve a single vacuole. However, most of them fail to survive the relocation following this and the next fission, so they are found in the posterior position very rarely. But, in some individuals they may survive and serve a single or separate vacuoles. In a certain clone of Paramecium aurelia multiple pores and vacuoles are rather frequent; these are, of course, the result of the tendency to produce multiple pores and vacuoles at the time of fission.

Morphology and Life History of Colpoda maupasi, Bensonhurst Strain

Abstract: Strains of Colpoda maupasi previously reported were found to produce only octogenic reproductive cysts and monogenic wrinkled resting cysts. The present form of C. maupasi (Bensonhurst strain), isolated by the senior author in 1949, was found to produce, in addition to the above, quadrigenic reproductive cysts, digenic corrugated (wrinkled) resting cysts, and smooth thick-walled monogenic, digenic and quadrigenic resting cysts. Some of the factors leading to the development of these cysts in the Bensonhurst strain are believed to be related to nutrition, age and size of the trophic forms. The cytological changes in encystment and excystment were followed with particular attention to aging monogenic resting cysts. The latter were observed for over 4 years.

Effects of Certain Metal Ions on Growth of Tetrahymena pyriformis

Abstract: Growth of Tetrahymena pyriformis in a peptone medium is inhibited slightly to extensively by comparable concentrations of oxalate, citrate, and ethylenediaminetetraacetic acid (in ascending order). Single additions of Ca, Cu, Zn, and Mg, in increasing order of effectiveness, reversed citrate inhibition. EDTA inhibition was completely reversed by single additions of Ca or of certain other metals (Al, Co, Cu, Fe, Mn, Ni, Zn) forming more stable EDTA complexes. Reversal by added Mg was slight. The data suggest physiological importance of Ca for T. pyriformis. Pre-treatment of peptone solution with a cation exchanger (Natrinil) resulted in little or no growth; growth was restored almost to normal by the addition of Mg. The growth-response showed a linear relationship to quantity of Mg.

Leucocytozoon in the Avian Order Columbiformes, with a Description of L. marchouxi Mathis and Leǵer 1910 from the Mourning Dove

Abstract: Leucocytozoon marchouxi is described from the mourning dove, Zenaidura macroura carolinensis in Illinois. The macrogametocytes are rounded or elliptical, measuring 7 to 11 by 8 to 15 microns (mean, 9 by 12 microns), and stain dark blue with Giemsa stain. The microgametocytes are often distorted or ruptured by the smearing process, but if not badly injured measure 5 to 11 by 8 to 15 microns, (mean, 8 by 11 microns). They stain pale blue with Giemsa stain. Host cell cytoplasm is rarely seen surrounding the microgametocytes, but was found in 26% of cells parasitized by the macrogametocytes. When present it forms a narrow border around part or all of the parasite's periphery, and is not drawn out to form elongate “horns.” The parasite was found in ten birds, of which five were adults, one was a juvenile, and four were nestlings. The infections were relatively light in the adults. The youngest bird in which the protozoon was found was 14 days old. The literature on Leucocytozoon in the avian order Columbiformes is reviewed. All forms with rounded gametocytes so far reported are considered to be L. marchouxi Mathis and Leger, 1910, of which L. turtur Covaleda Ortega and Gallego Berenguer, 1946, is considered a synonym.

Studies on an Astomatous Ciliate From a Fresh-water Limpet, Ferrissia peninsulae

Abstract: An astomatous holotrichous ciliate inhabiting the excretory tubule of the freshwater gastropod Ferrissia peninsulae is believed to be conspecific with Dogielella renalis Kay, found originally in the renal organ of an unidentified species of another pulmonate genus, Physa. The organization of the ciliary system and the arrangement of the contractile vacuole pores suggest that it is closely related to members of the hymenostomatous genus Tetrahymena, and that it has evolved from a ciliate of this general type through loss of the cytostome and cytostomal membranelles. Because it is not possible at present to state with certainty that this ciliate is congeneric with D. sphaerii, the genotype of the genus Dogielella Poljanskij, a new genus, Curimostoma, is established for it. Curimostoma is referred provisionally to the family Tetrahymenidae.

The Infection of Duck and Goose Erythrocytes by the Mammalian Malaria Parasite, Plasmodium berghei

Abstract: The infection of mice and baby rats by both Plasmodium lophurae, an avian parasite, and Plasmodium berghei, a mammalian malaria parasite, prompted investigation of the likelihood of P. berghei infecting avian erythrocytes. Though erythrocytes of chick embryos were not infected, those of the goose and duck embryos were. In both these cells the morphology of the parasite was markedly different from that seen in mammalian erythrocytes. Infections were transitory and it was impossible to find parasites after 4 days. Examination of the hosts of both species of parasites showed a rather wide range and examination of the susceptibility of the duck erythrocyte indicated that this cell was peculiarly receptive to infection by a variety of plasmodia.

Feeding Processes in Solenophrya micraster Penard 1914

Abstract: The feeding processes of Salenophrya micraster were studied and described in relation to the apparent selection of acceptable live prey ciliates, the feeding time in relation to the number of tentacles operative, and the contractile vacuole rate during feeding and subsequent reproduction. On the basis of these observations, the fundamental mechanisms involved in the suctorian feeding process are discussed.

The Morphology and Life Cycle of Solenophrya micraster Penard 1914

Abstract: Solenophrya micraster, originally collected from a strip mine pond in east-central Illinois, was established in clone cultures. From these homogeneous populations, detailed studies on the morphology and life cycle of the species were made. On the basis of the morphology established by these studies and a review of the species assigned to the genus by previous workers, emended diagnoses of genus Solenophrya Claparede and Lachmann 1859 and Solenophrya micraster Penard 1914 are proposed.

An Improved Method of Staining the External Organelles of Hypotrichs

Abstract: A simple, rapid method of staining the external organelles of hypotrichous ciliates is described. Specimens are fixed and stained with Noland's combined phenol-formaldehyde, gentian violet fixative and stain. The staining solution is displaced with iodized glycerine as soon as the external structures are stained to prevent it from coloring the cell body. Cirri and membranelles are stained jet black in sharp contrast to the clear amber background.

The Common Occurrence of Micronuclear Variation During Binary Fission in an Unusual Race of Paramecium caudatum

Abstract: Unstable micronuclear behavior was investigated in an unusual race of Paramecium caudatum. Lines were begun, after isolating single vegetative specimens, to yield mass cultures. After study of living specimens in the precision micro-compression chamber and permanent preparations stained with Feulgen and iron-hematoxylin, most paramecia revealed a single micronucleus but many were observed with two micronuclei and fewer with more than two micronuclei—occasionally three, rarely four. Specimens measured 225 microns in length; the micronucleus about seven microns. Instead of normal cyclosis, the protoplasm exhibited great fluidity. Generally two contractile vacuoles were present but specimens with three vacuoles, even four, were not uncommon. The method of producing amicronucleate specimens and those with variable numbers of micronuclei was discovered by studying large numbers of actively dividing paramecia. Instead of a micronucleus passing to each daughter at the end of fission as in normal animals, the entire late telophase stage of the dividing micronucleus is passed to the anterior or posterior daughter cell at the time of constriction of the cell. The result is that one daughter is bimicronucleate and the other daughter amicronucleate. Bimicronucleate and amicronucleate animals are capable of dividing normally. In bimicronucleate specimens, division stages show two micronuclei in late telophase stages that result in four micronuclei, two passing to each daughter cell. However, aberrations may again occur in fission to produce variations in number of micronuclei. The irregularly shaped, atypical, macronucleus may extrude chromatin or may undergo complete fragmentation (hemixis, type D). Paramecia and macronuclei may be parasitized by a microorganism which may cause this derangement of normal micronuclear events. This possibility of induction of micronuclear variation in Paramecium by foreign microorganisms may be of considerable evolutionary significance in the genus.