The host-response of the polynoid Polynoë scolopendrina Savigny, commensal with the terebellid Polymnia nebulosa (Montagu), is relatively specific within the family Terebellidae.

Evidence is presented that an unstable or closely bound attractant is present on the outside of the host and perhaps in tube material, but apparently absent in the mucus secreted by the host. Efforts to demonstrate its presence in ground-up whole host resulted in failure.

The polynoid Lepidasthenia argus Hodgson demonstrates a similar specificity of response to its host Amphitrite edwardsi Quatrefages.

The polynoid Harmothoë spinifera Ehlers, commensal with Amphitrite gracilis Grube, responds to the alternate host Polycirrus caliendrum Claparede as strongly as to its own host, and more strongly than to other species of Amphitrite. Likewise, Polynoë scolopendrina, commensal with Polymnia, responds with greater intensity to the alternate host, the eunicid Lysidice ninetta Audouin and Milne-Edwards, than to any non-host terebellid. This behaviour may be i terpreted as evidence that the specificity of at least some single commensal species for hosts which are not closely related to each other may depend upon the production of similar attractants by these hosts.

The responses of three commensal populations of Harmothoe lunulata (Delle Chiaje), commensal respectively with the ophiuroid Acrocnida brachiata (Montagu), the holothurian Leptosynapta inhaerens (O. F. Miiller), and the terebellid Amphitrite johnstoni Malmgren were tested against seven alternate hosts. Each gave maximum response to its own host. However, the population from Acrocnida responded as strongly to Leptosynapta as to its own host, while giving no responses at all to any of the other five.

Removal of the eyestalks in Leander serratus does not result in an earlier moult, a shorter intermoult period, or a higher moult rate. There is no evidence of an eyestalk moult-inhibiting hormone in this species. The evidence points to the existence of an eyestalk moult-accelerating hormone. The possible correlation of the presence of the moult-inhibiting hormone and seasonal moulting is discussed.

The sizes, length and breadth, of the cyprids of Balanus balanoides, B. crenatus and Verruca stroemia have been measured on material collected. during the spring outburst and in the later part of the year.

The size-frequency curves for Balanus balanoides and B. crenatus show at least two distinct modesduring the spring, equivalent to populations of two distinct sizes. It is suggested that these correspond to populations developed in different environments. Measurements of the nauplii taken from adults at different points on the shore indicate that the size of the nauplii is dependent to some extent upon the conditions of development, the conditions also affecting growth and total nauplii output.

Swedish samples, in which the parents had developed under more uniform conditions, showed only a single population as regards size.

In B. crenatus and Verruca stroemia, which produce further broods during the year, the size decreases in these later broods. The rate of development of the eggs and embryos, probably dependent upon temperature, is suggested as the important factor.

One hundred each of stage VI male and female and stage V Calanus finmarchicus were picked at random, and, by means of a projection microscope, measurements made on a number of segments in both metasome and urosome.

The stage VI female population was mixed containing 95% of a smallsized population and 5% of a larger size-group. The males constituted a single population.

At this time of the season the stage VI male and female metasomes are the same length, but there are differences in the sizes of the individual segments, the most striking of which is that of the head

The stage V animals in many of the measurements could be quite clearly separated into two size-groups of about 50% each and it is suggested that these are potential male and female populations. This separation at 50/50 has been noticed in numerous other collections of stage V, but it shouldbe emphasized that the differences are population differences in regard to those measurements considered.

Evidence is presented which shows that the state of the antennules after preservation in 5% neutral formalin is unlikely in stage V animals to be a reliable guide to their sex in the next stage.

A thin membrane surrounding the faeces of many of the Caridea has proved to be chitinous. The membrane is not secreted by the fore-gut, but almost certainly by the anterior part of the intestine, and is therefore a peritrophic membrane sensu stricto.

On the evening of 20 February 1953, two plaice (Pleuronectes platessa L.) in the largest tank of the Aquarium were observed spawning. No information on the spawning behaviour of pleuronectids has been found in the literature; nevertheless, the observation may very well not be original, but is considered of sufficient interest to justify an account of it.

The blood of Lophius piscatorius is poor in haemoglobin, the volume of red cells being only 17%. The plasma contains less than 40 g. of protein/1., of which only 6 7 % is albumin. This explains its low osmotic pressure. As is well known, it contains more crystalloids than mammalian blood, A(depression of freezing-point) being 0–84°, the same figure being found at Naples, Woods Hole and Plymouth. This rather high concentration is not due to organic constituents, that of total non-protein nitrogen being of the same magnitude as in mammals; it is mainly due to a high content of sodium chloride. Chloride is at a concentration of 15.3 m.equiv./1oo ml., sodium at 18.5, while in mammals they reach 9 and 15 respectively.

Total non-protein nitrogen concentrations in plasma are similar to concentrations in mammals; themain non-protein nitrogen constituents of plasma are neither urea, ammonia, uric acid or allantoin, but trimethylamine or trimethylamineoxide. Of our analysis 37% of non-protein nitrogen of plasma remain unidentified, so far as we can rely upon our chemical methods. The power of concentration of the kidney for non-protein nitrogen on the whole is not high; it varies up to fifteen times. But the degree of concentration by the kidney, small for most constituents, even for trimethylamine, seems to be very high for creatine which is the main representative of non-protein nitrogen. Of our urine analysis, 30% of non-protein nitrogen remain as yet unidentified.

Lophius kidneys perfused with the heparinized blood (venous) of the fish secrete urine in which total non-protein nitrogen is concentrated, magnesium highly concentrated, and chloride only slightly so or not at all. Oxygenation of the blood, or lowering the temperature of the perfusate from c. 20° to c. 5° C. does not appear to influence secretion. The blood flow through the kidneys increases with the perfusion pressure, the increase often becoming disproportionately large. The urine flow, on the other hand, above a certain critical level is largely independent of changes in perfusion pressure.

Laboratory experiments showed that freshly liberated Spirorbis larvae settle on surfaces which bear previously settled individuals, in marked preference to bare controls, but that larvae which have been kept swimming for 3 hr., or longer, exercise less choice when setting.

When larvae are freshly liberated there is a great difference between the rate of setting gregariously, and the rate of setting in isolation; but after they have been kept swimming for 3 hr. this difference becomes less, owing to the larvae setting more rapidly both gregariously and in isolation. After swimming for about 8 hr. rates of setting fall off, and many larvae fail to settle, apparently through weakness.

I am greatly indebted to Dr D. J. Crisp for advice regarding this problem, and to him and Mr G. M. Spooner for much help with statistical treatment.

A description is given of a new type of apparatus designed to sample plankton from the immediate vicinity of the sea bottom, and purely from this region. Details of the construction are given and the relative merits of the design are briefly discussed.

It could be used for quantitative hauls.

A small additional net serves to sample the smaller benthic fauna at the same time as bottom plankton is being sampled.

An examination of Hodge's original slides of marine Acari shows that three alterations in synonymy are called for: (i) Simognathus sculptus (Brady, 1875) to become a synonym of S. minutus (Hodge, 1863); (ii) Copidognathus oculatus Hodge, 1860 to become C. oculatus Lohmann, 1889; (iii) C. glyptoderma Trouessart to become a synonym of C. granulatus (Hodge, 1863). Observations were also made on the permanence of Dean's Medium as a mountant for small arachnids and some quotations and observations on the value of certain diagnostic characteristics of the genus Copidognathus are made.

Munro Fox (1926, Addendum, p. 219) described a method of preparation of chlorocruoroporphyrin from the blood of the marine polychaete worm Spirographis. This was based upon the very troublesome method of Nencki & Zaleski (1900), which is time-consuming and wasteful. Furthermore, Spirographis is not easily obtainable in this country. Lemberg & Parker (1952) started with protoporphyrin, and by careful oxidation with potassium permanganate in acetone obtained a solution which gaVe mixed crystals of chlorocruoroporphyrin and diformyldeuteroporphyrin esters. Purification was by fractional chromatography. The procedure to be described here is simple and rapid, and could easily be carried out in one day by a biologist requiring a small sample of the porphyrin. The two methods mentioned above would not come into this category.

This work was done at the Plymouth Laboratory, and I am very grateful to Mr T. R. Tozer of that laboratory for so kindly obtaining the animals for me and extracting the blood.

The polychaete worms Myxicola infundibulum, Sabella pavonina and Branchiomma vesiculosum are all readily obtained from the muddy shores of the Salcombe estuary, especially on the Salstone. Blood was taken directly from the vessels of about 100 assorted worms by syringe, and squirted as it was removed from the worms into a mixture of peroxide-free ether (3 parts) and ‘Analar’ glacial acetic acid (1 part). After all the blood had been added, the mixture was well shaken and allowed to stand in the ice-chest for 30 min. The acetic acid was then washed out with distilled water, the first few washings containing a little sodium acetate to avoid washing out of the pigment, and the remaining solution of chlorocruorohaematin dried roughly by filtering through ether-soaked paper into a distilling flask and evaporated to dryness. 100 ml. of a 50% solution of hydrazine hydrate in glacial acetic acid were then added, and the mixture heated on a water-bath at 90° C. for 10 min.

If Arion hortensis be fed on a diet which contains 90Sr, autoradiographs show that the isotope istaken up by the digestive and lime cells of the digestive gland. From the former it passes to th haemocoel; in the lime cells it is concentrated around the calcium spherules. Some of the tracer enters the body through the wall of the intestine. Calcium stores which surround blood vessels and calcium cells in the mantle also concentrate the tracer.

In Aplysia.punctata 90Sr from the surrounding water passes through the surface of the body, and especially the gill; in Acanthodoris pilosa ions which enter the tissues from the sea water accumulate around the numerous calcium concretions in the mantle. These marine molluscs obtain cations directly from the water as well as by way of the food.

There is a slow uptake of strontium ions by the ctenidia of Mytilus edulis, though, even in filtered sea water, the gut is the more important area for their ingress to the body. It is possible that they enter with the mucous feedingsheets. They pass readily into the cells of the digestive gland. Some of the isotope taken in with the food is absorbed by the wall of the intestine; this also occurs in Patella vulgata, in which the intestine provides a much larger area, and in Lepidochitona cinereus.

Mytilus placed in filtered sea water which is activated with 90Sr, so increasing the strontium content by 007%, show the tracer localized for excretion within 10 hr. Ions are aggregated in the pericardial glands, not in the kidney.

An apparatus in which it is possible to observe the horizontal migrations of zooplankton in gradients of phytoplankton is described, and an account given of its use in experiments involving various organisms. A preliminary search for toxic organisms is also described.

The experiments comprise a demonstration of a migration by various animals into concentrations ofthe diatoms Skeletonema, Thalassiosira, Biddulphia, Nitzschia and various mixed cultures and the flagellates Chlamydomonas, Peridinium, Dicrateria, K, and Oxyrrhis. Cultures of Rhodomonas and Gymnodinium II are found to produce the opposite effect, and no reaction towards Lauderia, Coscinodiscus, Eucampia, Syracosphaera and Exuviaella could be shown. Results with bacteria cultures andvarious inorganic gradients are also discussed.

A second apparatus in which it is possible to observe the vertical migrations of zooplankton in the presence and absence of phytoplankton is also described, and an account given of experiments in it involving various organisms.

The experiments comprise a demonstration that greater numbers of animals swim up in the presence of mixed phytoplankton cultures, Coscinodiscus, Skeletonema, Ditylum, Chlamydomonas, Gymnodinium I and II and Oxyrrhis than in unenriched water. Flagellate One has no effect and Chlorella possibly depresses the number swimming up.

Under-water observations on the swimming movements of some of the animals used are described. The possible application of the observations towards resolving the problem of the inverse distribution of phytoplankton and zooplankton in the sea is discussed, and the hypothesis is proposed that this may be accounted for by a combination of migration and grazing. It is considered that plankton animals must migrate both horizontally and vertically into patches of phytoplankton and, when present in sufficient numbers, graze these down very quickly.

During 1946 and 1947, regular samples of Mytilus edulis from a number of localities ontheBritish coasts, including Conway, Brancaster and Liverpool, were examined for gonad conditionand spawning. For each sample, the mean stage of gonad development was computed. The criteria employed in distinguishing the stages of gonad development are described.

Ripening of the gonads takes place within a few weeks of the onset of spawning, in general commencing when the sea temperature has risen above 7–0° C. There appears to be no correlation between nutritional condition and ripening of the gonads, or subsequent spawning.

In all localities and in each year in which observations were made spawning occurred in late spring (mid-April to the end of May) and in most areas lasted for a short period only (2–4 weeks). At Brixham, in 1949 and 1950, the duration of the spawning period was longer (4-6 weeks). In most cases, 70–80% of the mature population spawned during the first 7–10 days of the breeding period. No evidence of periodic spawning was obtained.

In all cases, spawning commenced in a period during which the mean temperature to which the mussels were exposed was rising from c. 9–5° C. to 11–12–5° C. In most cases, the onset of spawning was coincident with a period of spring tides, and of predominantly bright sunny weather. The initial rate of spawning appears to be directly related to the rate of increase in mean temperature to which the mussels are exposed.

After spawning, mussels enter into a ‘neuter’ or ‘resting spent’ stage in which all traces of sexuality are lost.

An account is given of the general structure of the body skeleton of the spatangid larva. A considerable change occurs in the skeleton as the larva increases in size, some parts being absorbed and new parts appearing. Of particular interest is the replacement of the anterior transverse rod by the ventral horizontal rod.

The skeletons of larvae, young stages to late stages, of Echinocardium cordatum, E. flavescens, Spatangus purpureus and Brissopsis lyrifera are described. The larvae of Echinocardium and Spatangus are, in essentials, very similar; that of Brissopsis differs greatly from them. A striking difference is that in Brissopsis the ventral horizontal rod arises from the postoral arm and anterior to the anterior transverse rod, in the other two genera it arises from the body rod posterior to the anterior transverse rod.

The replacement of the anterior transverse rod by a ventral horizontal rod is probably normal in clypeastroid larvae also.

A method of demonstrating cellulose utilization in biological systems by measurement of the turbidity of a cellulose suspension in a photo-electric absorptiometer is described. The crystalline styles of Ostrea edulis and Mytilus edulis appear to contain a cellulolytic factor as yet uncharacterized.

This preliminary list of some of the classes of the algae has been prepared, mainly for the use of British phycologists, to form a basis on which to work for the eventual compilation of a complete check and locality list of all species of British marine algae. The compiler would be grateful for all additions and corrections to this list, and for records of marine species from the algal classes not included in the present list.

The classes of algae treated in this list are the Chlorophyceae (53 gen., 156 spp.), Xanthophyceae (7 gen., 15 spp.), Chrysophyceae (15 gen., 22 spp.), Phaeophyceae (96 gen., 199 spp.), Rhodophyceae (126 gen., 324 spp.), and Cyanophyceae (39 gen., 125 spp.). The genera are listed alphabetically under the family and the species alphabetically under the genus. If a name has been changed from that given in Newton (1931), the name in Newton is added, in brackets, below. Names preceded by a question mark appear to need revision for nomenclatural or taxonomic reasons. Most of the so-called varieties listed are very probably merely habitat forms of the species, but further investigation is needed before new combinations are made for them. Notes are given at the end of each class, the number in brackets following a name in the list refers to these notes.

The compiler is grateful to Mr R. Ross and Miss Linda Newton, of the British Museum, and to Miss C. I. Dickinson, of the Herbarium, Kew, for their help over a number of problems.

Patron

The Council has pleasure in reporting that His Royal Highness The Duke of Edinburgh, K.G., has graciously consented to become Patron of the Marine Biological Association of the United Kingdom.

The Council and Officers

Four meetings of the Council have been held during the year, three in the rooms of the Royal Society and one at Plymouth. At these the average attendance was seventeen. The Association is indebted ‘to the Council of the Royal Society for the use’of its rooms.

The Council has to record with regret the deaths of two Vice-Presidents, Viscount Astor and Dr W. T. Calman, C.B., F.R.S.; of Dr Th. Mortensen, an Honorary Member of the Association; and of Prof. J. H. Orton, F.R.S., sometime member of Council and for many years a member of the Staff of the Plymouth laboratory.

Thé Plymouth Laboratory

Following the completion last year of the building of the laboratory for research with radioactive substances, the opportunity has been taken of paving the area between this laboratory and the main building with concrete.

The facilities of the main workshop have been improved by the purchase of a milling machine.

The Council is grateful to the Development Commissioners for the supply of a new Morris 10 cwt. truck.

The Aquarium

Throughout the summer months the aquarium was crowded with visitors, and their appreciation and interest is reflected in the sale of large numbers of the aquarium guide book. Tanks have been stocked to capacity, perhaps the most notable exhibits being the wreck-fish {Polyprion americanus), mentioned in last year's report and now in fine condition, and about twenty boar-fish {Capros aper), which make an especially colourful display.