Showing papers in "Journal of the Marine Biological Association of the United Kingdom in 1961"

Synopsis of the Medusae of the world

Abstract: This work was started many years ago in the form of a card-index for my own use. At the beginning the building up of the index involved a great deal of work, but later on it saved me time for my studies, and it was not difficult to keep it up to date. One day my friends, Dr F. S. Russell, director of the Marine Biological Laboratory, Plymouth, and Dr W. J. Rees, British Museum (Nat. Hist.), London, saw this index, and they repeatedly urged me to put it into a form suitable for publication for the benefit of other students of medusae. I agreed, though hesitatingly, because my time was much occupied. A grant from the Browne Research Fund of the Royal Society of London, however, enabled me to employ an assistant, Mr J. Liitzen, who under my supervision could carry out the necessary revision and the typing, as well as some translation from Danish or other languages into English; he has done it remarkably well, and I wish to thank him for his industrious and painstaking collaboration.

The bottom fauna of the English Channel

Abstract: A survey has been made of the bottom fauna in ca. 10–50 m along the south coast of England, using a modified anchor-dredge. Particular attention has been paid to the molluscs (both living and dead) and to the echinoderms, only larger or more conspicuous members of other groups being identified.Within the Channel there are considerable variations in temperature and other hydrographic conditions, and these are discussed in relation to their possible role as limiting factors in distribution. The fauna and bottom deposits of the different areas covered in the survey are briefly described.Distribution trends are classified as:(1) Species generally distributed in the Channel. This is the largest group, and includes three species reaching their northern limits in British waters.(2) Species confined to the western parts of the Channel.(a) Western species. Four or five species common at Plymouth in the 1920's, but now absent or very rare. Small numbers are found today only off the south Cornish coast, and those which occur in the North Sea are restricted to the north-western areas. Apart from one species, these forms are not at their geographical limits in the English Channel, and their occurrence may be partly related to the presence of ‘western’, but not necessarily Sagitta elegans, water.(b) Cornubian species. These are near the northern end of their range, and occur quite commonly off the south Cornish coast, becoming progressively less common farther up-Channel. It is suggested that their distribution is related to an intolerance of the lower winter temperatures in the more eastern part of the Channel.

The Behaviour of Macoma Balthica (L.)

Abstract: The tellinid Macoma balthica moves extensively about the surface of the sand, its activities not being restricted to vertical movements as hitherto supposed.These horizontal migrations comprise a movement towards the sun followed by a movement away from it. If there is heavy cloud movements still occur, in summer at least, but are at random.Other intertidal species indulge in similar movements, possibly indicating a widespread habit which confers the advantage of bringing the animal into contact with surrounding areas while maintaining its station on the shore.

The Buoyancy of the Cuttlefish, Sepia Officinalis (L.)

Abstract: The excess weight in sea water of the living tissues of Sepia officinalis (L.) is approximately balanced by the cuttlebone, which accounts for about 9·3% of the animal's volume. The density of cuttlebone varies around 0·6. The cuttlefish without its cuttlebone would be about 4% denser than sea water.The chambers of the cuttlebone are independent of one another but liquids and gases are free to move within any one chamber.Animals caught and studied fresh aboard ship exhibited a much less wide range of cuttlebone densities than those kept in an aquarium.Specimens kept in aquaria vary greatly in buoyancy. These variations result from changes in density of the cuttlebone.Cuttlebones differ not in the weight of dry matter per unit volume, which is always close to 38%, but in the amount of liquid they contain. A cuttlebone of density 0·7 contains about 30% liquid whereas a cuttlebone of density 0·5 contains about 10% liquid. The remainder of the cuttlebone contains gas, but this gas is at less than atmospheric pressure. The pressure of gas varies around 0·8 atmosphere. Within the duration of the experiments described here, the mass of gas per unit volume of bone remained almost constant whatever the bone's density. The pressure of gas is lower the less dense the cuttlebone. There can be no question of an evolution of gas expelling liquid from a bone when it becomes lighter. The constancy of the mass of gas within the cuttlebone is explained in terms of the slowness of diffusion of gases into the bone.

Age, growth, and reproduction of the rock goby, Gobius paganellus L., in the Isle of Man

Abstract: Age, growth and reproduction of the intertidal teleost, Gobius paganellus, has been investigated in the Isle of Man from March 1959 to September 1960. Samples were obtained by poisoning shore pools with a rotenone emulsion.Age was determined by examination of otoliths where a translucent annual ring is laid down in spring. Although the potential life span is at least 10 years, immature fishes of the first two age-groups constitute most of the population. An onshore breeding migration is postulated. An empirical survival curve indicates a high mortality rate during the first two years of life. Instances of predation on G. paganellus are given.Growth in length is logarithmic, with marked decrease in growth rate from about the age of sexual maturity. During the year, growth occurred from June to October. Maximum standard lengths recorded were 92*5 mm (feThe overall sex ratio of females to males was 1:1-326; this predominance of males persisted through the age-groups. The reproductive organs are briefly described, and a classification of gonad maturation is proposed. The breeding season lasted from mid-April to mid-June. Sexual maturity was reached at the end of the second or third year of life. Smallest ripening individuals found were 48-5 mm (female) and 505 (male). Fecundity increased with body size. Eggs were deposited on stones in shore pools and guarded by the male. Post-larvae occurred in pools from the beginning of July, and the first demersal individuals from August. Size-frequency distribution of oocytes in the ovary indicates that at least two broods may be produced in a single breeding season.In maximum size, longevity, and age at maturity, G. paganellus differs from other European gobies so far studied. It is suggested that a similar life history is exhibited by other British species of Gobius. The short breeding season of G. paganellus in the Isle of Man is held to be a result of proximity to the northern limit of distribution of this species. Examples of this phenomenon in other teleosts are provided. The significance of pre-ovulatory corpora lutea in the ovary of G. paganellus is briefly discussed.

Reproduction, Growth and Mortality of Venus Striatula (Da Costa) in Kames Bay, Millport

Abstract: Seasonal changes in the gonads of both sexes of Venus striatula were followed by macroscopic and microscopic examination, in over 700 animals from a population consisting mainly of one year-group. The sex ratio was approximately equal, and no hermaphrodite adults were found.

The functional morphology of the British species of Veneracea (Eulamellibranchia)

Abstract: The functional morphology of twelve British species of the Veneridae is described. The systematic position of Mysia undata and evolution within the Veneracea are discussed.Structurally, the members of the family Veneridae show a lack of special adaptations. The ability to move horizontally as well as ventrally in soft substrata is retained; the pedal gape is large and the foot well developed. The siphons are relatively short and fused. The food-collecting mechanisms of the mantle cavity are largely unspecialized and function in maintaining a considerable flow of water, and retaining as much as possible of the suspended material. Members of the Veneridae show a considerable uniformity of structure, but trends of evolutionary change may be distinguished. The genera Gafrarium and Callista are least specialized. The genus Dosinia has evolved along an independent line and is specialized by the possession of a stream-lined, circular shell, deep lunule, and greatly elongated siphons, for a relatively deep-burrowing habit. Within the superfamily Veneracea major lines of adaptive evolution have given rise to the rock-boring Petricolidae and the deep-burrowing Glaucomyidae, and the genera Venerupis and Irus show affinities with both these families.

The ultra-violet absorption of sea water

Abstract: Measurements of the ultra-violet absorption spectra between 200 and 400 mix, have been made with a spectrophotometer. At short wave-lengths natural sea water has double the absorbancy of artificial sea water. The difference in samples from shallow depths is ascribed to organic material, of which part may be the Gelbstoff of Kalle. Regional variations have been found, coastal waters having higher U.V. absorptions. A small seasonal effect with an increase in absorbancy in summer in the English Channel has been seen. In deep Atlantic water increased absorption below 235 m/x may be due to its high nitrate concentration. At longer wave-lengths absorbancies were less than in surface waters. Measurements of U.V. absorption may supplement other physical methods of characterizing water masses.

Quantitative differences in the fauna of boreal mud associations

Abstract: The fauna of a muddy area in the northern North Sea (the Fladen ground) is compared with that of a similar area in a Scottish west-coast sea loch (Loch Nevis). These areas were selected because certain similarities in environmental features and in fauna, coupled with their marked difference in biomass, make them particularly suitable for studies of the factors affecting benthic production.For macrobenthos samples (from a grab) a coarse sieve with round holes of 1-3 mm diameter and a fine sieve with meshes of 0-5 mm side were used. Meiobenthos samples (from a corer) were sieved through a 0124 mm mesh and the total residue stained in rose bengal.The Fladen ground, depth 140 m, had annual bottom temperatures between 6-31 and 8-22 C and salinities between 35-20 and 35-2.50. The deposit was mainly of coarse silt with abundant tests of small Foraminifera. The fauna is redescribed. The characteristic species was the foraminifer Saccammina sphaerica. By separating empty tests from living specimens it is shown that this species was not so abundant as had been thought. The main lamellibranch was Thyasira equalis, not T. flexuosa as recorded in previous work. Other important species were the polychaetes Paraonis gracilis, Myriochele heeri, Spiophanes kroyeri, Tharyx sp., Lumbrineris impatiens, and Nephthys incisa. The standing crop of macrobenthos was 6-42 g/m2 wet weight.

The effect of light on the buoyancy of the cuttlefish

Abstract: The behaviour of well fed cuttlefish is strikingly affected by light. When the light is bright they usually bury themselves in the gravel at the bottom of their tanks, whilst after twilight they come out of the gravel and swim around until dawn.Cuttlefish kept in complete darkness for one to two days usually become so buoyant that they are incapable of staying on the bottom and can only remain in mid-water with difficulty.Animals kept in artificial light and dark showed changes in density which could amount to 2%. These changes come from changes in the volume of the gas space within the cuttlebone.The density of the cuttlefish is largely governed by light intensity and there is little indication of an inherent diurnal rhythm of density change.The rate of uptake of liquid when the cuttlefish becomes denser is such that it is unnecessary to assume that any active process is used to pump liquid into the cuttlebone. The cuttlefish must, however, extract liquid actively from the cuttlebone to become less dense.

The Distribution of Gas and Liquid within the Cuttlebone

Abstract: The newest chamber of a cuttlebone is always incomplete and full of a watery solution. This contains sodium and potassium in concentrations close to those of sea water.The second newest chamber contains a gas space and sometimes contains liquid. This liquid is rarely localized at the siphuncular end of the chamber. It is not certain that liquid is initially extracted through the siphuncular wall of the chamber, although this is possible.When liquid is pumped out of a newly formed chamber the salt which it initially contains is not left behind, either free or bound into the structure of the bone.The 3rd to about the 10th newest chambers usually contain no visible liquid. But their siphuncular walls are permeable to liquid and liquid does enter these chambers when the cuttlebone becomes very dense.At cuttlebone densities around 0·6, i.e. close to values which will make the cuttlefish neutrally buoyant, the older and more posterior chambers are almost full of liquid. This liquid can, however, be pumped out. When a cuttlebone has a density around 0·5 very little liquid can be seen in any of its chambers.The pressure of gas within a newly ‘pumped out’ chamber is very low, but by the time a chamber has become the ninth newest the pressure of gas is close to the average value for the whole cuttlebone, i.e. about 0·8 atm.The low pressure of gas found in the newest chambers is explained by the slowness with which gas diffuses into a space created by the active removal of liquid.

The Osmotic Mechanism of the Cuttlebone

Abstract: Experiments are described which test the hypothesis that the cuttlefish controls the relative volumes of gas space and liquid within its cuttlebone by an osmotic mechanism acting across the siphuncular surface of the bone. When the animal is at the bottom of the sea it would maintain the gas space within the cuttlebone by balancing the hydrostatic pressure of the sea by an osmotic force between the liquid within the cuttlebone and the blood.In cuttlefish kept for some weeks in shallow water in an aquarium all the liquid taken from the cuttlebone is almost isotonic with the animals’ blood.In animals recently hauled from the bottom of the sea the cuttlebone liquid is markedly hypotonic to sea water and hence to the blood.These lower osmotic concentrations are given chiefly by reduction in the concentrations of the sodium and chloride ions.After bringing animals up from about 70 m to the surface of the sea the osmotic concentration of the cuttlebone liquid rises from about 75% of sea water some 40 min after starting to haul the trawl, to about 97% of sea water 6 h later. Extrapolation back to the time at which hauling began gives a concentration of salts close to that predicted by the osmotic hypothesis.Whilst the cuttlebone liquid is increasing in ionic concentration the liquid deeper in the cuttlebone is hypotonic to that just inside the siphuncular surface. This is explained in terms of the slowness of exchange of salts along the narrow channels between the lamellae of the cuttlebone.

On the Biology of Calanus Finmarchicus XII. The Phosphorus Cycle: Excretion, Egg Production, Autolysis*

Abstract: It is shown that equilibrium of 32P throughout the body of Calanus is reached only after a feeding period of about a week. The time required to liberate by excretion the amount of P present in a Calanus is about 20 days. Fed Calanus excrete at a higher rate than starved. The implications of excretion in feeding experiments using 32P is discussed.There are large differences in the total P content of individual Calanus. Figures are given for ripe and unripe females, fat and lean Stage V, and eggs. A high percentage, up to 55% of the total P, may be lost by excretion during starvation.A high proportion of the P in the food assimilated (up to 70%) may appear within a week as eggs laid.Liberation of P from dead Calanus is very rapid and is almost complete in three days.The relation of excretion and autolysis to the P cycle in the sea is discussed.

The behaviour of polydora ciliata (Johnst.). Tube-building and burrowing

Abstract: Polydora ciliata is a spionid polychaete found below mid-tidal level burrowing in a variety of rocks all of which contain calcium carbonate. It can also penetrate some non-calcareous materials such as rotten wood. It excavates a U-shaped burrow which it lines with a tube composed of mucoprotein and sand grains. This tube has a smooth inner lining of mucoprotein. Both food and tube-building material is collected by the palps and it is suggested that discrimination is made chiefly on size of the particle. Selection is made between the limits of 003-0-05 mm, the smaller particles passing down the gut whilst the larger are used in construction of the tube. A particle selection mechanism is suggested. The function of the segmental mucus glands is to provide the inner lining of the tube.The problem of chemical penetration of rocks by animals is discussed. P. ciliata uses both mechanical and chemical methods. No acid has been identified, and the use of a sequestering or chelating agent linked with the biochemistry of mucus is suggested.

Salinity Tolerance and Permeability to Water of the Starfish Asterias Rubens L.

Abstract: Evidence is presented to suggest that the salinity tolerance of the adult North Sea Asterias rubens is around 23‰, whereas that of the Baltic Sea animals is 8‰. This, together with other evidence outlined, is thought to be sufficient reason to justify the use of the term ‘physiological race’ where these two populations are concerned.Adult A. rubens from the North Sea is incapable of any degree of weight regulation in diluted media within the ecological temperature range, size or state of the breeding cycle.Similarly, it is incapable of any osmotic regulation and it is suggested that the two main coelomic cavities constitute an osmotic unity.

On the nutrition and metabolism of zooplankton I. Preliminary observations on the feeding of the marine copepod, Calanus helgolandicus (Claus)

Abstract: Measurements have been made of the quantity and type of food assimilated by adult female Calanus helgolandicus (Claus) during the summer months.Animals kept in the dark at 10° C under a continuous flow of ‘outside’ Plymouth sea water (0·95–2·50 mg insoluble organic material/1.) removed 26·0–66·5 μg/day/Calanus, of which 74–91% was actually digested.Volumes of sea water filtered daily varied between 10·0 and 36·0 ml./ animal, with an average of 21·5.The animals preferentially selected a diet of high organic content from the particulate food available, digesting average daily quantities of 18·1 μg carbohydrate, 6·5 μg lipid and 2·7 μg protein.The average amount of food digested daily accounted for 25·3% of the dry weight and was equivalent to an average respiration rate of 26·5 μl. O2/ animal/day, which adequately accounts for the highest values reported by others for C. finmarchicus (Gunnerus) kept under similar conditions of light and temperature.These results, which provide direct evidence that Calanus obtains the bulk of its food from particulate material present in the sea, have been discussed with especial reference to Putter's hypothesis.

Studies on the biology of limpets IV. The breeding of patella depress a pennant on the north Cornish coast

Abstract: The breeding of Patella depressa was studied at Trevone, North Cornwall, for 4 years. Gonads were examined and assessed by methods described in a previous report on P. vulgata.In contrast to the common Limpet, P. depressa is a summer breeder in Cornwall. Gonad development begins in the spring and is complete by June or July. Spawning coincides with maximum air temperatures in July, August or early September. The autumn and winter period is passed with gonads in recognizable post-spawning and spent stages, and only a small proportion of completely resting neuter gonads is found in the early spring.Mass spawning takes place, and gametes are voided rapidly. No definite spawning stimulus can be shown, but, as with P. vulgata, there may be some relation between onset of spawning and the occurrence of wave action on the shore.The differences in breeding behaviour of P. depressa and P. vulgata reinforce the other differences between them and throw some doubt on the concept of super-species in Patella.

Further Observations on the Fine Structure of Chrysochromulina Ericina Parke & Manton

Abstract: C. ericina Parke & Manton has been re-investigated to add salient features of micro-anatomy from the electron microscopy of thin sections and also to add photographs of living cells taken with anoptral contrast light microscopy.The most important new observations concern the scales which are shown to be essentially two-layered plates in which the layers in the very large spined scales have become separated except at their edges, with the outer layer greatly hypertrophied to produce a hollow spine with a flared base closed at the bottom by a flat plate. The patterns of external marking on the two layers are very similar in both plate-scales and spines in this species and the orientation of both with respect to the cell surface has been demonstrated by a section of the scales in situ.

Studies on Ectocarpus in Culture II. Growth and Nutrition of a Bacteria-Free Culture

Abstract: The growth and nutrition of Ectocarpus confervoides has been studied in bacteria-free cultures. Growth was estimated by dry weights determined under controlled conditions. A method for inoculation of cultures of filamentous algae is described and a table of culture media is given. Following a lag of 5–7 days there was a period of growth, which was not truly exponential, extending over a period of 35 days. Calculation of the relative growth constant for the early stages of growth indicated that the alga doubled its dry weight every 6–7 days. Cultures of Ectocarpus remained viable for over 1 year in the light and for over 100 days in the dark. In natural sea-water media the maximum growth was brought about by the addition of 0·5 mM potassium nitrate and 0·1 mM potassium phosphate. Ferric chloride had no effect on growth but additions of manganese chloride did cause some stimulation. Additions of some complex organic mixtures slightly increased growth but Ectocarpus was unable to grow on a range of organic carbon source in the dark. The optimum salinity at 20° C was somewhat higher than that of natural sea water but was apparently lower at 15° C. The optimum pH was 8·0. Light intensities between 1350 and 16,000 lux had no marked effects on the growth rate but did effect the lag, the optimum for this being 7000 lux. Temperature also had no effect on the growth rate but did effect the lag. The optimum was 15–20° C but there was growth between 10 and 25° C. A considerable range of artificial sea waters, with and without organic additions was investigated, in no case did they give a yield greater than two-thirds that in natural seawater media. These results are discussed in relation to other workers findings.

Biological differences between sea waters: experiments in 1960

Abstract: The years which have elapsed since we first published on this subject (Wilson, 1951) have seen much confirmation that, in the laboratory, the development of the sea-urchin (Echinus esculentus) and of other species is influenced by some unknown property or properties of sea water, which varies from one locality to another and in the same locality from time to time, and can vary with depth at the same station. The property would appear to be linked with the distribution and movements of oceanic and coastal water masses, but of what it consists we have as yet no certain knowledge. We have tested various hypotheses, our own and others propounded to us, but so far every such test has been negative. Recently Bougis (1959) has suggested that copper concentration in sea water, which is known to be variable in distribution and in time, could explain our results. He supported his hypothesis with careful experiments in which he reared larvae of Paracentrotus lividus in sea water to which copper sulphate was added to increase the copper concentration to desired amounts. He found that with increasing copper concentration the size range of arm-spicule length was reduced. A significant reduction was obtained with concentrations equivalent to those known to occur in natural sea water; the reduction was evident at 5 fLgfl. Cu, and it was well marked at 10 fLgfl. Cu and above. Bougis quoted figures for copper concentrations from several parts of the world giving ranges from 1 to 34 fLgfl. Cu. In particular he quoted figures from Atkins (1953) showing an annual variation for surface water at station El from 1'5 fLgfl. Cu in autumn to 24.8 fLgfl. Cu in winter. Other figures from Atkins were quoted, including a contrasting pair for E 1 on 13 April 1949 when the surface water showed 8'1 fLgfl. Cu and the deep water at 50 m showed 18'3 fLgfl. Cu. He rightly pointed out that the copper concentrations for the waters we used had never been determined. He wrote and asked if it were possible for us to verify his hypothesis, and in view of his work this seemed a very reasonable request. Earlier than Bougis, Bernhard (1957) had shown similar effects of copper on the development of Arbacia lixula larvae and he had published photographs showing a great difference between Arbacia larvae reared in water from the Gulf of Naples and in the same water after chelation. In the latter the larvae were normal, in the former abnormal.

Further Observations on the Fine Structure of Chrysochromulina Minor and C. Kappa with Special Reference to the Pyrenoids

Abstract: Chrysochromulina minor and C. kappa have been re-investigated by means of electron microscopy of thin sections to add details of the microanatomy of pyrenoids and haptonemata, and by anoptral contrast light microscopy to study pyrenoids in living cells. In both species the pyrenoid is in the form of a diverticulum projecting from the centre of the inner face of a plastid and, in C. minor , strongly flexed to lie along it. In C. kappa the pyrenoid is commonly enveloped by the nucleus which may conceal it entirely from view in life. Some details of the behaviour of the surface membranes of plastids and pyrenoids in relation to that of the nucleus are given. The haptonema structure in both species is shown to be comparable to that of others in which this appendage is much longer, though an occasional variant with eight instead of seven central fibres or tubes has been encountered in C. kappa and is demonstrated. The presence of ‘peculiar’ Golgi structure is reported for both species and demonstrated for C. kappa . Some direct evidence indicating an internal origin of scales from vesicles is demonstrated in C. minor . Finally a summary is given of salient structural criteria for all the described species attributed to this genus from the marine plankton, the closest agreement as regards pyrenoid structure in the two species under investigation being with C. chiton .

Vitamin B 12 and Marine Ecology: The Response of Monochrysis Lutheri

Abstract: Yield of the supra-littoral chrysomonad Monochrysis lutheri varied directly as vitamin B 12 concentration between the limits 0·1 and 100 μμg/ml., each μμg of vitamin supporting 0·55 × 10 6 cells. Between the same limits of concentration there was to be seen no significant deviation in initial rate of cell division from the mean value of 1·1 divisions per day (phototrophic growth: 2000 lux, 20° and 15° C), the conclusion being that limitation of the division rate does not occur before the concentration vitamin B 12 has dropped below 0·1 μμg/ml.

Notes on the mode of life of the Tellinidae (Lamellibranchia)

Abstract: Ten species of Tellinidae occur in British waters, belonging to the genera Arcopagia, Tellina, Gastrana and Macoma (Winckworth, 1932, 1951). This paper is concerned only with Arcopagia crassa, and the commoner species of Tellina: T. squalida, T. tenuis, T. fabula, T. donacina and T. pygmaea. These species burrow in sands, muds or gravels, maintaining connexion with the overlying water through their long and extensile siphons. Some account of the habitat of individual species is given by Yonge (1949). The majority of burrowing lamellibranchs occupy a more-or-less vertical position when buried, but a few (e.g. Cochlodesma, see Allen, 1958) lie horizontally beneath the surface. While studying dispersal in a population of T. tenuis (Holme, 1950), it was noticed that the majority of specimens excavated at low tide lay on their sides, but it was not at the time appreciated that they always lay with one side, the right, uppermost. Yonge (1949) assumed that members of the Tellinidae occupy a vertical position when buried, but he is of the opinion (personal communication) that T. tenuis makes considerable vertical movements in the sand according to the state of the tide, so that the position in which it is found at low tide may be rather different from that when covered by water. Both MacGinitie (1935) and Fitch (1953) record that the North American shore clam Macoma nasuta lies on its left side, the posterior end of the shell, which is curved to the right, being inclined upwards, so that it seemed possible that other members of the Tellinidae might show similar habits. Observations on the habits of the Tellinidae have been made as follows: (a) on the position of animals dug up at low tide on the shore, (b) on the method of burrowing, (c) on the shape of the valves.

Shell form in Venerupis rhomboides

Abstract: Two forms of Venerupis rhomboides occur in Plymouth waters. A more slender form, corresponding to that described by Pennant, occurs in the Eddystone shell gravel, and a more robust form, corresponding to the Venus sarniensis of Turton, occurs at the mouth of the River Yealm. The two forms differ in ratios of shell height, width and lunule width relative to shell length. A population with intermediate ratios is found at 6-5 m in Plymouth Sound.Plots of height/length ratios of these and another intermediate sample on probability paper did not indicate that the intermediate populations were composed of mixtures of the two extreme forms, and it was provisionally concluded that these were all variants of a single species.If the height/length ratios of series of samples from different localities are plotted against depth of water on a logarithmic scale, an inverse relationship, approaching a straight line, is obtained. Regression lines for median ratios in the 3-4 and 4-5 cm length groups have been plotted separately, as there is some change in proportion with increasing length. These show a highly significant negative correlation between shell ratios and depth.From the regression lines it has been possible to obtain an estimate of the depth inhabited by even quite small samples of shells. Depth estimations have been made for eight samples, consisting mainly of dead shells. Six samples lay within the expected limits, and discrepancies in the other two samples are attributed to transport along the sea floor.The possible causes of the differences in shell ratios are discussed. Previous work suggests that shell ratios may be affected by different rates of growth. Soil grade, temperature, food supply, and light penetration are considered unlikely causes of the observed differences in shell ratios, and it is suggested that the pattern of growth may be affected by pressure.The Appendix contains a key to British species of Venerupis.

The Larval Stages of Balanus Balanus (L.) Da Costa

Abstract: Six naupliar and a cyprid stage for B. balanus are described and diagrams given for the general outlines and individual appendages. Sizes and setation formulae are given.The naupliar stages resemble both B. balanoides and B. crenatus; attention is drawn to some distinguishing features and a key for the separation of the species is provided.