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.

Inspection of fauna lists suggests that many authors have found difficulty in identifying the British species of Thracia, most being content to list them as Thracia spp. Examination of museum collections and even keys to identification (Ziegelmeier, 1957) shows many errors of identification. The problem was brought to notice when some specimens dredged off the Northumberland coast appeared to differ from the five species recognized as occurring in British waters. It was decided that a study of the specific differences similar to that of Holme (1951, 1959) for Ensis and Lutraria, and Allen (1954) for Nucula, would be useful.

Specimens, particularly undamaged ones, of the British species of Thracia are difficult to obtain because they are both fragile and rare, and I am greatly indebted to the many people who were so kind as to give material and information for this study. These included Mr J. H. Barrett, Dale Fort Field Centre; Dr C. Burdon-Jones, Marine Biology Station, Menai Bridge; Mr I. C. J. Galbraith, British Museum (Nat. Hist.); Prof. R. A. R. Gresson, Queen's University, Belfast; Prof. L. A. Harvey, The University, Exeter; Mr N. A. Holme, Marine Biological Association, Plymouth; Dr N. S. Jones, Marine Biological Station, Port Erin; Mr A. D. Mclntyre, Scottish Home Department, Aberdeen; Mr R. McLaughlin, The University, Aberdeen; Dr R. H. Millar and Dr R. B. Pike, Scottish Marine Biological Association, Millport; Mr A. M. Tynan, Hancock Museum, Newcastle upon Tyne. I also wish to thank Dr D. A. Edwards, King's College, Newcastle upon Tyne, for assistance in matters mathematical.

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.

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.

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.

Experiments are described in which attempts were made to fertilize eggs of the lugworm taken from the coelom. These were unsuccessful except when the eggs were taken from spent or partially spent worms or from worms kept in the laboratory until they were about to spawn. It was concluded from this that maturation of the eggs precedes spawning but only by a matter of hours. That maturation begins in the body cavity was confirmed by histological examination of eggs from partially spent worms and criteria are given for the recognition of immature and mature eggs. Lack of success in previous attempts to fertilize coelomic eggs from non-spawning worms may be because females which are just about to spawn are not obtained by the normal methods of collection. It is suggested that this is due to a change in the behaviour of the worms associated with retention of eggs in the burrow after oviposition. With regard to the stimulation of spawning in female worms, it has been shown that maturation immediately precedes the onset of shedding. This, together with the fact that if eggs undergoing maturation are injected into a nonspawning worm they are shed automatically suggests that the primary stimulus for the onset of shedding is, simply, one which will induce maturation of the eggs.

Observations made during the above experiment together with the fact that worms can be induced to shed a few unripe eggs by injection of tissue extracts suggest, however, that spawning is not entirely passive and dependent on maturation. The lipid fraction of tissue extracts stimulates the active uptake of eggs from the coelom but it fails to induce maturation of the eggs and hence the free spawning produced in male worms. While the release of lipid into the body cavity may have some effect on the spawning of female worms (under natural conditions) similar to that previously suggested for males, it cannot provide the primary internal stimulus for spawning.

A brief account is given of the sessile animals and algae found by diving on the Lulworth Banks. The numbers of a sponge, a sabellid worm and bryozoari were counted over a total area of 650 m2.

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.

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.

The effect of salinity upon the wood-boring activity of Limnoria was investigated experimentally. Boring decreased linearly with salinity and ceased altogether below io%o. The limiting salinity varied inversely with the temperature, being 12%0 at 17-6 C and 15 %0 at 14-9 C (average temperatures). The boring activity was intensive in its early stages but after about 5 weeks fell to a lower constant rate.

Survival experiments suggested that the low salinity was the direct cause of the reduced boring activity. The only lethal salinity found during the period of the experiments (65 days) was 6%0 which proved fatal in about 15-20 days. The next higher salinity tested was i2%0. No reduction in survival was found in concentrated salinities up to a value of 48 %0, the highest salinity examined.

An hypothesis has been erected to account for the failure of the Plymouth herring fishery and the associated biological events in the early thirties. It was found that the quantity of winter phosphorus was inversely related to the quantity of pilchard eggs 6 months earlier and directly to the quantity of herring recruits a year earlier. It is thought that the differences in quantities of winter phosphorus have represented differences in numbers of 6-month-old pilchard larvae; the winter phosphorus provides the link between herring recruitment and numbers of pilchard eggs, suggesting that there has been competition between the herring and pilchard stocks, in their juvenile stages. Thus it is suggested that the Plymouth herring fishery failed in competition with the pilchard stock and that the other biological events which took place in the early thirties were a consequence of this postulated competitive change.

The use of tetraphenylarsonium chloride for the detection and determination of perchlorate in sea water has been investigated. An aqueous solution of this reagent gives a visible precipitate of tetraphenylarsonium perchlorate with sea water containing 5 μg ClO4-/ml. within 10 min. For the quantitative determination of traces of perchlorate, potassium perrhenate is added to the water sample, and the tetraphenylarsonium perrhenate, which is precipitated by addition of the reagent, co-precipitates tetraphenylarsonium perchlorate. Perchlorate is determined in the mixed precipitate by infra-red absorption spectrophotometry. Using 100 ml. of sea water, a sensitivity of 0·03 μg ClO4-/ml. can be attained, with a coefficient of variation of ca. 10%. No interference is caused by the ions normally present in sea water.

Styela mammiculata breeds during the summer, probably in August and September. Some eggs are self-sterile. Embryos show a yellow crescent of presumptive muscle cells. The larvae hatch by means of an enzyme. The larval sensory apparatus includes a large unicellular otolith and a small ocellus, which is composed of a single pigmented retinal cell and a single lens cell.

of winter phosphorus have represented differences in numbers of 6-month-old pilchard larvae; the winter phosphorus provides the link between herring recruitment and numbers of pilchard eggs, suggesting that there has been competition between the herring and pilchard stocks, in their juvenile stages. Thus it is suggested that the Plymouth herring fishery failed in competition with the pilchard stock and that the other biological events which took place in the early thirties were a consequence of this postulated competitive change.

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.