Showing papers in "The American Naturalist in 1922"

Coefficients of Inbreeding and Relationship

Abstract: IN the breeding of domestic animals consanguineous matings are frequently made. Occasionally matings are made between very close relatives-sire and daughter, brother and sister, etc.-but as a. rule such close inbreeding is avoided and there is instead an attempt to concentrate the blood of some noteworthy individual by what is known as line breeding. No regular system of mating such as might be followed with laboratory animals is practicable as a rule. The importance of having a coefficient by means of which the degree of inbreeding may be expressed has been brought out by Pearl' in a number of papers published between 1913 and 1917. His coefficient is based on the smaller number of ancestors in each generation back of an inbred individual, as compared with the maximum possible number. A separate coefficient is obtained for each generation by the formula

Variation Due to Change in the Individual Gene

Abstract: THE present paper will be concerned rather with problems, and the possible means of attacking them, than with the details of cases and data. The opening up of these new problems is dne to the fundamental conitribution which genetics has made to cell physiology witlhin the last decade. This contribution, wliclh has! so far scarcely been assimilated by the general physiologists theemselves, consists in tlhe demonstration that, besides the ordinary proteins, carbohydrates, lipoids, and extractives;, of their several types, there are present within the cell thotusands of distinct substances--the \" genes \"; these genes exist a.s ultra-microscopic particles; their influences nevertlheless perme-ate the entire cell, and th-ey play a fundamental role in determining the nature of all cell substa.nces, cell structures, and cell activities. Through these cell effects, in turn, the genes affect the entire organism. It is not mere guesswork to say that the genes' are ultra-microscopic bodies. For thie work on D-osophila has not only proved that the genes are in the chromosomes, in definite positions, but it has shown that there mnst be, hundreds of such genes within ea,ch of the la.rger chromosomues, although the length of tlhese clhromosomes is not over a, few microns. If, then, we divide the size of the chromnosome by the minimum number of its genes, we find that the latter are particles too small to give a visible image. The chemical composition of the genes, and the formulm of their reactiois, remilaimi a.s vet quite unknown. We do know, for example, tlhat in certain ca.ses a given

Variations in the Number of Vertebrae and Other Meristic Characters of Fishes Correlated with the Temperature of Water during Development

Abstract: FOR several years I have been studying the correlations between altered environmental conditions and the number of vertebrT and other segmentally arranged structures in fishes. Johannes Schmidt, of the Carlsberg Laboratory in Copenhagen, has been carrying on a series of intensive investigations (see bibliography) which deal with the same problem, and which are for the greater part rather closely paralleled by my own studies. Both of us have obtained, independently, a rather large volume of experimental and observational evidence indicating that the meristic characters displayed by an individual fish a-re determined not alone by heredity, but in part also by the environmental conditions, particularly temperature, which prevail during some sensitive developmental period. II

Variations in Datura Due to Changes in Chromosome Number

Abstract: Two forms with which we ha.vTe recently carried on breeding experiments, the garden flower Portulaca and the jimson weed (Datura Stramnoniumn), are strikingly different in the types of variations which they show. The Porttulaca is procurable in a wide range of color varieties, and is apparently subject to relatively frequent mutations, both seminal and sonmatic, with sectorial and periclinal chimeras a common phenomenon. Sufficient breeding tests have been made to indicate that the varieties of Portulaca are due in large measure at least to gene nmutations. In comparison with Portutlaca, the jimson weed is relatively stable so far as gene mutations are concerned. Despite the large amount of breeding work with this species, both before and since the rediscovery of Mendel's law, only the two allelomnorphic pairs of characters, purple vs. white flowers, and spiny vs. smooth capsules, have been identified aside from the pair, tall vs. short stature recently determined by the writer and Avery (3). It is true that certain of our pure lines of Datura differ slightly from others when grown in comparable pedigrees, but the fact remains that so far as sharply contrasting Mendelian characters are concerned, .the jimson weed! is highly stable, while the Portulaca is highly mutable. Our knowledge of changes in chromosome number in other forms is not sufficient o indicate if there is any significance for the present discussion in the difference just mentioned between Portttlaca and Datura. Our interest in Datura began about 1910 or 1911, when the jimsons were used as demonstration material for students in genetics. In 1915 we found our first mutaiit which we ca.lled the Globe fronm the shape of its capsules.

The Assortment of Chromosomes in Triploid Daturas

Abstract: The present article is the one of a number of proposed papers which will deal with the behavior of the chromnosomes in the different classes, of Datura mutants, the correlation of the chromosomal differences with changes in structural and other characters, and with the ratios in which Mendelian allelomorphs are found in the offspring. The method mainly used in the microscopical examination, and the general principles involved, are given in two papers already in press for THE AMERICAN

Complete Linkage in Drosophila melanogaster

Abstract: When the entire amount of water has passed through the filterpaper, the latter is removed, spread out, and immersed in a bath of water, in a watch crystal. The water should just cover the filter-paper. The device shown in Fig. 2 is now brought into play. This consists of a glass pipette, flattened and spread at its tip, and serves admirably for gently scraping and sucking the surface of the filter-paper, as it lies in the watch crystal. This withdraws into the pipette the organisms which have been filtered out. These can now be transferred to a glass slip and examined under the microscope, or injected into culture media as inoculations. The writer has found that, with practice, the possibilities of the micro-filter may be extended to aid, in many ways, in the study of the protozoa. LEON A. HAUSMAN

Crossing-Over Involving three Sex-Linked Genes in Chickens

Abstract: agents. Those which lived to produce young gave rise exclusively to normal young, indicating that genetic changes were not responsible for the abnormal heads. However, in view of the known inheritance of eyelessness in cave arthropods and vertebrates and in Drosophila melanogaster, it seems of interest to examine each case of profound eye modification in crustaceans and elsewhere to gain information on the origin and inheritance of any possible mutation of this character.4

The systematic location of genes by means of crossover observations

Abstract: IN the construction of a chromosome map, the distances between neighboring genes are equated to the percentage of crossovers which have been observed between them. Owing to errors of random sampling, and sometimes to other disturbing causes, inconsistencies always arise between the distances so determined. For example, in the important data given by Lancefield and Metz for the sex chromosome of Drosophila willistoni [1, p. 241] we have the following values:

Experimental Studies on the Duration of Life. II. Hereditary Differences in Duration of Life in Line-Bred Strains of Drosophila

Abstract: IT was shown in the first paper in this series (27) 2 that there was a marked difference in mean duration of life, and in the form of the curve, between wild-type stocks of Drosophila on the one hand and the syntheuic quintuple mutation stock on the other hand. It was further made clear that, because of the technique used in the experimental work, there could be no doubt that the basis of this difference must be hereditary and not environmental. Furthermore, Hyde (11) and Pearl (6) have presented evidence for the Mendelian inheritance of this character duration of life. Given it to be the fact, as the just cited work demonstrates to be the case, that there are hereditary differences within the same species of Drosophila in respect of duration of life, the problem which next presents itself is to determine whether within a particular strain of Drosophila hereditary differences exist, and if so what their magnitude may be, their degree of permanence, etc. In

The Sound-Transmitting Apparatus of Salamanders and the Phylogeny of the Caudata

Abstract: RESEARCHES by Kingsbury and Reed, extending through a number of years, have shown that the soumd-transmitting apparatus of salamanders consists of two elements. These are the columella and the operculum. In the most recent paper on this subject, Reed (1990) gives a resume of all the previous work, an extensive account of the state of affairs in the Plethodontidce, a brief account of the conditions in other forms, and the findings are presented in the form of a family tree. The purpose of the present article is to add an account of the condition of the apparatus in two forms not seen by Reed, to question the condition described by Kingsbury and Reed for Dicamnptodon ensatus (Ambystomna te11.ebrosum Auct.), to suggest a somewhat different interpretation of the facts observed by them, and to proposed a somewhat different phylogeny, which seems to agree quite as well with the otic apparatus and far better with other anatomical features. Kingsbury and Reed (1909) were unable to examine any of the Asiatic forms related to Hynobius. These forms, as Cope pointed out long ago, are rather different from the Anbystomide, with which they have usually been associated, and should in fact form a family THyno biid-e. I have recently been able to examine large series of Ilynobius leechii from Korea. This animal shows a condition of the otic apparatus different from any seen by Kingsbury and Reed, and a condition which I am compelled to consider primitive. Both columella and oper-

Experimental Studies on the Duration of Life. IV. Data on the Influence of Density of Population on Duration of Life in Drosophila

Abstract: FAIRLY early in our experimental work on duration of life in Drosophila it became apparent to us that the number of flies per bottle, or, since the bottles used are of uniform size, the density of population, had some influence on the mean duration of life of the flies, when other environmental conditions are constant. Such a relationship might reasonably be expected a prior, from what is known of the influence of this factor on human death rates, commonly expressed as Farr's Law (cf. Farr, W. (35), Brownlee, J. (36, 37)), and on other biological functionls, such as growth (Semper, K. (38), Bilski, F. (39)), resistance to poisons (Drzwina and Bohn (40)), rate of reproduction (Pearl and Surface (41), Pearl and Parker (42)), etc. As soon as it was recognized that this variable, density of population, might influence our experimental results with Drosophila, care was taken in setting up experiments to make this a constant in each case. At the same time the records of the earlier work were carefully re-examined to determine what part this variable may have played in the results. Happily it was found that in none of our work so far published upon the duration of life in Drosophila had density of population varied enough to have any appreciable effect upon the results or conclusions. As was recently pointed out by Pearl and Parker (42), however, \"there can be n o question that this whole matter of influence of density of population, in all senses, upon biological phenomena, deserves a great deal more

The Sex-Linked Group of Mutant Characters in Drosophila willistoni

Abstract: Twenty-eight recessive sex-linked mutant characters in Drosophila willistoni are described and their linkage relations considered. 2. In general, the genetic behavior of willistoni (as regards crossing over, etc.) is similar to that of D. melanogaster and the other species of Drosophila whose genetic behavior is known. 3. There is a strong indication of parallelism between the mutants yellow and scute in willistoni and yellow and scute in melanogaster. 4. In both species these characters are completely or very closely linked. 5. There is some indication of parallelism between the characters forked and stubby in willistoni and singed and forked in melanogaster. 6. In melanogaster the genes for yellow and scute are "located" at one end of the chromosome map, and singed and forked are 21 units and 56.5 units respectively from this end. In willistoni yellow and scute are near the middle of the map, and forked and stubby are on one side at 12 units and 42 units respectively. 7. Since the X-chromosome of melano...

Experimental Studies on the Duration of Life. V. On the Influence of Certain Environmental Factors on Duration of Life in Drosophila

Abstract: In experiments involving the determination of the duration of life in 2,990 individual flies, it was found that there was no prolongation of the life of Drosophila produced by adding embryonic juice (either from the chick, or from the larvae of Drosophila itself) daily to the food, to the amount of 2 per cent. of the total food material, beginning with the 31st day of the flies' life.

The Nature of Bud Variations as Indicated by Their Mode of Inheritance

Abstract: THE title limits this accounit to such bud variations as have been studied critically with respect to their iniheritance in sexual reproduction. The further limitation of time makes it necessary that I choose from among such studies certain cases to serve as illustrations of the several types of bud variation. I shall, therefore, attempt no complete review of the researches bearing on the problem at hand. A survey of published accounits of bud-variation studies shows that as yet comparatively little is definitelv known of the real nature of these vegetative sports. It seems not unlikely, however, that to poilit out some of the problems suggested by these studies anid, where possible, to note modes of attack may serve the purpose of this symposium quite as well as a rehearsal of knowii fadts and their interpretation. As here used, the term bud variation is syioillv11ous with vegetative as contrasted with seminal variation. The term somatic variation may also be employed to the same effect, provided it is niot thereby intended to exclude cases in which the germ tract as well as the soma is involved. At the outset, however, there must be imposed on any of these terms, for the purpose of this discussionl at least, the limitation that the variation involves a change in the genetic constitution of the parts affected. The expressions somatic mutation anid somatic segregation are specific terms and as such are niot to be used interchangeably with the more general terms somatic, vegetative, or bud variations. Moreover, to speak of a particular vegetative variation as a case of sonmatic muta1 Paper No. 94, Departmiient of Plant Breedinig, Cornell University, Ithaca, Nn11 -vlk--

On Rearing Sexually Mature Ptaynereis Megalops From Eggs

Abstract: THE literature affords so few cases of marine animals reared under laboratory conditions that the writer ventures to communicate his successful attempts to carry through to sexual maturity the nereid, Platynereis me galops, from eggs laid in the laboratory. This work had its origin in a suggestion made by Dr. F. R. Lillie in 1911 that the capacity for cross. fertilization between Nereis limbata and Platynereis mnegalops be tested. At that time, however, since we knew so little of the life history of these forms, we felt that it was necessary to get all data possible on each life history in order to have a standard of comparison for the life history of the hybrids. So far all efforts to cross these nereids have failed. The difference in the breeding habits of Nereis and Platynereis is so striking that this alone might account for the failure of cross fertilization. Nereis sheds eggs into the sea-water where fertilization takes place; Plattynereis lays inseminated eggs soon after -copulation. However, this very difference is calculated to enhance the interest attaching to the cross fertilization. It might be possible to study the inheritance of the egg-laying reactions. In addition, early observations revealed that the young Platynereis megaylops closely resemble Nereis dmmerili. Since, as is well known, Nereis dclmerilii has a complex life history, we felt that the life history of Platynereis might well repay study for its own sake.

Is There a Transformation of Sex in Frogs

Abstract: THIS paper is a, reply to the recent article of Dr. Emil Witschi which appeared in a late issue of the NATURALIST (Vol. LV, No. 641). Witschi is quite convinced that the problem of sex development and differentiation in frogs has been settled, and that nothing further remains to be said. However, the writer feels that instead of being solved, the time has come for a revision of the entire question of sex development in Anurans, and that the subject is ripe for a reinterpretation upon a more ra, tional basis than that accorded to it heretofore. The firstt portion of the paper will be devoted to a brief exposition of the writer's interpretation of sex in frog larvae based upon data obtained from a study of the bullfrog. The second part of the paper is a, reply to certain questions raised by Dr. Witschi. In larval males of the bullfrog two gonads are: formed, just as there are two kidneys formed, a pro-testis or embryonic sex gland destined to degenerate and disappear in ontogenetic development and a definite or functional testis which replaces it. The germinal elements of the pro-testis arise in the entodserm and migrate into the germ ridges early in embryonic life. The cells multiply rapidly and together with the mesodermal elements of the germ glands form paired ridges projecting into the ccelomic cavity. While the tadpole is very immature and has yet a. year of larval life before metamorphosing, the

Experimental Studies on the Duration of Life. III. The Effect of Successive Etherizations on the Duration of Life of Drosophila

Abstract: IN any experimental work of a genetic character on Drosophila, it is often necessary to anesthetize the flies which are to be used in an experiment for a sufficiently long time so that they may be sexed and sorted into different groups for the purpose of making matings,, etc. It has been shown by Morgan (33) that this procedure has no effect upon the causation of morphological mutations, the inheritance of which he has studied (9). The effect might, however, conceivably be quite different in the case of a physiological character like duration of life. Any one who has undergone a major surgical operation feels that anesthetization is at least immediately a rather profound physiological disturbance. Unfortunately, so far as we are aware, no accurate determinations have ever been made to show whether in man one or more anesthetizations changes the expectation of life. As a. matter of fact, there are presumably no human data on the point available in any such amount as! would be necessary for actuarial determinations, because in man anesthetization is, generally speaking, only undertaken in connection with surgical operations of greater or less severity, so that if we did have statistics of expectation of life of persons who had been anesthetized, there would always be involved the two factors of anesthetization and oper-

Orthogenesis as Observed from Paleontological Evidence Beginning in the Year 1889

Abstract: THE Origin of Species is now clearly understood in the hard parts of invertebrates and of vertebrates, and there is little to be added as to the nodes of mechanical evolution No chances or experiments are tried by Nature. The process is continuous, adaptive, mechanically perfect in every Mutation of Waagen. As showl in. actual observations by all close students of vertebrate and invertebrate morphology during the last fifty-two years, and as summed up in the remarkable contribution of 1) 'Arcy Wentworth Thompson (1917) on \"Growth and Form,\" animal mechanisms compete with each other in close analogy to humanly made machines-automobiles, typewriters, aeroplanes. Consequently, while Nature is constantly standardizing her machines through individual competition and producing flocks of birds and shoals of fishes which are so precisely alike that animals of the same age, sex, environment and heredity show no perceptible variation, she is also frequently substituting more perfect and more adaptable machines and discarding older and less adaptable ones, exactly as man is doing in the case ofhis automobiles, his typewriters, and his aeroplanes. Thus the naturalist and the paleontolog-

A Fourth Allelomorph in the Albino Series in Mice

Abstract: IN recording the occurrence of a new mutant gene in the house mouse, allelomorphic to color and albinism, Detlefsen ('21)2 described a very dilute, wild form in which the hair showed traces of a light brownish tinge with a suggestion of sootiness, and the eyes were somewhat less heavily pigmented than in the wild type. This general form of pigment reduction is also characteristic of other color allelomorphs; for in the case of the ruby-eyed rat, the ruby-eyed guinea-pig and the chinchilla rabbit (Castle '21) ,3 the yellow pigment is very greatly reduced or even obliterated, while the darker pigments (black or brown) are at least slightly modified. The mutant mouse, however, showed a far greater pigment reduction than either the rat, guinea-pig or rabbit mutants. Breeding tests demonstrated 'that this dilute mouse mutant was a color-albino allelomorph, and in this respect resembled the ruby-eyed rat and guinea pig genetically (the chinchilla rabbit had not been recorded at that time), but Dr. Detlefsen pointed out that \"it is hardly safe to insist that these mutations are identical. ... We are also unable to prove that they are different, for the genes may be identical but simply give different somatic effects, since the residual inheritance can not be the same.\" tHe also suggested that the discovery of a new dilute type of mouse (which he was seeking at that time), more like the rat or guinea pig in its somatic appearances as well as in its genetic behavior, would give us more assurance that his extreme dilute mouse mutant was not. the homolog of the ruby-eyed rat or guinea pig. Unusual as it may seem, I had discovered exactly such a new dilute mutant mouse in January, 1919. By comparing it with Dr. Detlefsen's set of rodent skins and by testing it in appropriate matings, I recognized its genetic significance just before his paper appeared in print. The discovery of this new mutant mouse enables us to say at once that the extreme dilute mutant was not the homolog of the ruby-eyed rat or guinea pig or the chinchilla rabbit, and supports Dr. Detlefsen 's position in hesitating to homologize

Orthogenesis and Serological Phenomena

Abstract: As my discussion progresses I fear that some of my hearers may be reminded of the old joke about the mongoose. A stranger carrying an odd-looking box was asked by a man whose curiosity got the better of his good manners, what was in the box. The stranger replied that it was a mongoose and went on to explain that his brother was subject to delirium tremens, during the attacks of which he believed that he was being strangled by snakes; this mongoose was to catch the snakes. To the reminder by the inquisitive man that these were imaginary snakes he retorted, " Yes, I know, but this is an imaginary mongoose." Since some. of our most competent investigators in the fields of genetics and evolution are skeptical apparently about the whole question of orthogenesis, to them, at least, I shall be making an imaginary attack upon a mythical phenomenon. President Kofoid, however, seemed to think that some of the recent work with immune sera done in my laboratory, which strongly indicates the induction of permanent germinal modifications, might have possible theoretical implications bearing on the question of orthogelnesis, and I agreed to discuss the subject, although realizing at the outset that the net result would not be a scientific proof, but merely a suggestion which might possibly be of some value as, one of various working hypotheses. First as to orthogenesis itself; is there such a process? Our answer must depend largely upon how we define orthogenesis. It takes but a glance at the literature of the subject to see that it has meant many different things to many different people, ranging from a, mystical inner 116

An Observation on the "Cluster-Formation" of the Sperms of Chiton

Abstract: AN OBSERVATION ON THE \" CLUSTER,-FORMATION)\" OF THE SPERMS OF CHITON 1 WHILE engaged with an inquiry into the natural history of the chitons, in 1918,2 I several times made an observation which may have a bearing on the significance of sperm-clusters, and on the mechanism of their formation. The matter could not at the time be adequately investigated, but since I shall not soon be in a position to examine it further my observations are here related for what they may be worth. The species concerned is Chiton tuberculatus Linn., an intertidal form quite abundant at Bermuda. It is necessary to note, first, certain features of the breeding process, which seems to me to have heretofore been 1 Contributions from the Bermuda Biological Station for Research. No. 119.

A Gene for the Extension of Black Pigment in Domestic Fowls

Abstract: The progenies of the brachytip-adherent-ramose hybrid furnish evidence that the ramose character may belong to the same linkage series, though the linkage is rather loose. Although the tassels of ramose plants are much larger than those of normal plants and it seemed not unreasonable to expect adherent-ramose tassels to present a large thickened mass, nothing of the sort was found and the ramose-adherent plants could be separated from the normal-adherent plants only by examining the ears. White and colored seeds were planted separately, but the percentage of the three characters are essentially alike, as is shown by the following figures indicating that all three are independent of one of the aleurone factors:

Linkage in Peromyscus

Abstract: STUDENTS of Mendelism are beginning to display the same interest in possible homologies between the genetic factors or \"genes\" of different species of animals or plants which the morphologists of thirty years or more ago did in homologies between organs. In considering a given case of suspected homology between genes, two criteria are, so far as I know, employed: (1) Resemblance between the developed characters which are attributed to the action of supposedly homologous genes. Mere similarity of appearance, however, is recognized as an extremely fallible criterion of homology here as in the case of comparative anatomy. (2) Agreement between the \"cross-over\" value shown by a pair of linked factors in one species, as compared with the corresponding value shown by supposedly homologous factors in another species. If both of the two linked genes under consideration are found to have much the same somatic effects in the two species, and if, furthermore, the degree of linkage is approximately the same in the two cases, the argument is strong for a twofold homology. Metz' and Sturtevant2 have been investigating the parallel mutations of several species of Drosophila, and it is not unlikely that this genus will furnish the best material for the study of genie homologies, just as it has shown incomparable superiority for certain other lines of genetic research. For rodents, what appear to be parallel mutations have been shown to occur among numerous species, even ones

Studies on Fish Migration II. The Influence of Salinity on the Dispersal of Fishes

Abstract: 1. Fundulus heteroclitus is able to discriminate toxic from non-toxic salts at a temperature and stream flow the same as the control. 2. Variations in temperature or in stream flow profoundly influence the reactions and are more powerful factors in the behavior of the fish than presence or absence of salinity. 3. In the apparatus used, errors due to the notable reactions of fish to currents of water have been reduced by presenting the control and experimental flows parallel to each other.

Inheritance of Plumage Color in Crosses of Buff and Columbian Fowls

Abstract: The Columbian plumage coloration in domestic fowls is distinguished from buff coloration by the presence of a gene S which determines the restriction or inhibition of buff pigments from the feathers. This gene is sex-linked, and dominant over its allelomorph s, which permits the development of buff pigment. 2. Fowls with the Columbian coloration do not differ from buff fowls in any single gene governing the development of black pigment. Multiple genes appear to determine the difference in the amount of black pigment developed. 3. Columbian and buff fowls are genetically alike in plumage pattern, that is, in the ability to develop black pigment in the feathers of certain areas (hackle, wing and tail feathers). 4. The buff coloration appears to have diverged from the Columbian coloration, or the reverse, by a single gene mutation affecting the development or inhibition of buff pigment; and by the accumulation through artificial selection of multiple genes for the development of black pigment in the Columbia...

Further Notes on the Paleontology of Arrested Evolution

Abstract: THE writer has in a former paper' endeavored to follow up the causes of persistence as: seen from the side of the paleontologist. Using as a basis the genera which appear in Zittel-Eastman's Textbook of Paleontology (1913) and defining as persistent all genera which pass through more than two periods, the following data relative to number of persistent genera (A), total number of genera cited (B), and percentage of persistent genera (C) were obtained: