It has been shown that there is a lunar periodicity in reproduction of P. opercularis near Plymouth in 1927-28. The ripening of sexual products corresponds with the full phase of the moon.

The condition and shape of the gonad changes with the development of the tissues.

The colour, too, of the hermaphrodite organ changes with development.

Black pigmentation has been observed on the gonad in thin-shelled P. opercularis, a phenomenon apparently due to actinic rays penetrating the thin shell.

The breeding season is from January to June inclusive.

The gut contents seem to show no appreciable difference either in quantity or in the natureof the food during a lunar month.

The moonlight has apparently no effect on the lunar periodicity in reproduction.

It is suggested that in the animal there is a physiological rhythm that causes the development of the gonad to coincide with the full moon of each lunar month

1. The larva of a Terebellid which is very common in plankton from the Plymouth district during spring has been reared and proved to be the young of Loimia medusa Sav. This larva is characterised by its very large gelatinous tube.

2. The development of the external structures is described from a stage in which the first tentacle was just appearing to a juvenile stage in which all the main characters of the adult had been assumed.

3. The building of the first sandy tube on the bottom is described.

4. The development of the bristles and uncini are dealt with in some detail and a comparison made with the corresponding development in Nicolea zostericola. Evidence of the suppression of a pair of larval bristle-bundles in Loimia is indicated.

5. Previous records of Loimia larvse are discussed.

6. McIntosh's separation of our British Loimia to a new species, L. montagui, is shown to be probably unjustified.

1. Regeneration from different levels in the polychæt worm Chætopterus variopedatus has been studied.

2. Regeneration can occur posteriorly from any segment, but anteriorly only from segment XIV forwards.

3. Where regeneration occurs at all, given sufficient time, it will be complete, i.e. the original segments occupy in the new worm the relative position they originally occupied in the old worm.

Normal healthy oysters with openings drilled in both inhalent and exhalent chambers, remove considerable amounts of glucose from solution. The average diminution in 5 experiments, each consisting of two such animals kept in 4 litres of sea-water containing about 0-2% of glucose, was 8-17% at the end of 36 hours.

In similar experiments, using the same oysters after their mouths had been plugged with wax and plasticine, there was only an average diminution of 1-4:6% in the glucose at the end of 36 hours. In two of the experiments there was no diminution, and in the three others there was evidence that one of the two oysters in each had been incompletely plugged and glucose had passed into the alimentary canal.

Oysters which had been plugged for 8 days so that they were bleeding profusely, the mantle cavity containing vast numbers of leucocytes, were used for a third set of experiments in which the average diminution was 7-4% at the end of 36 hours.

There was no evidence of bacterial decomposition of glucose within the experimental period.

These results, taken with those of previous investigations, show that the ciliated epithelia of Lamellibranchs cannot absorb (nor ingest phagocytically). Absorption takes place in the tubules of the digestive diverticula within the alimentary canal, and, in the mantle cavity, only through the agency of phagocytes which are extruded in great numbers when Lamellibranchs bleed as a result of bad conditions.

The opinion of Ranson that Marennin and other soluble matter is absorbed directly by the ciliated epithelia in the mantle cavity cannot be upheld, this material being deposited in the cells by the phagocytes which either absorb it directly from the mantle cavity and gut, or transport it from the digestive diverticula.

There has existed in the past, and still does exist, considerable confusion both in the question of a satisfactory basis for the classification of ascidians and that of the validity of many species.

The principal orders and families are fairly stereotyped, and confusion and divergent opinion is mainly confined to the internal classification of the various families. These differences have a twofold origin, in that classifications have been constructed by various authors on three distinct bases, and that it is very difficult to distinguish between structures which are similar through relationship and those which are similar through convergent or parallel development. Further difficulty arises from the fact that authors describing a new species with a view to fitting it into one particular classification, have often given insufficient details for its accurate inclusion in another scheme. There is also divergent opinion as to the correct nomenclature that should be employed, but with that this paper is not concerned.

The following two sections represent two preliminary communications to the study of relative growth in a small Crustacean admirably adapted for use as a laboratory animal in all studies involving growth and development.

The present paper deals with the results of investigations into certain phases in the life-history of the bivalve mollusc Tellina tenuis carried out during the autumn of 1926 and 1927.

Collections in the intertidal zone and below L.W.M., were made in a number of bays in the Cumbrae and neighbourhood, Kames Bay, Millport, being selected for intensive study.

In Kames Bay Tellina tenuis ranges from a little below H.W.M. to depths of about 4 fm. The maximum concentration of about 1000 per sq. m. is found at L.W.M. springs and the numbers decrease to zero at H.W.M. and 4 fm.

In Kames Bay the density of Tellina tenuis falls in a progressive manner from L.W.M. to H.W.M.

The size-frequency distribution shows a regular gradation from the lower to the higher levels. At L.W.M. and below individuals of small size predominate, while at H.W.M. they are proportionately few.

At higher levels growth is more rapid than at the lower levels.

The size-frequency curves and density of Tellina tenuis in the other bays at L.W.M. correspond with those of half-tide in Kames Bay.

The rate of growth may therefore be influenced by the density of population as well as by the habitat.

In all areas the 1926 brood predominates.

The Tellina tenuis population in Kames Bay seems to be composed of four year-groups, one of which is almost unrepresented. Collections from neighbouring bays indicate that older groups may be present.

The amount of young brood on the bottom seems to vary considerably from year to year, being large and small in alternate years.

The two closely related species, T. tenuis and T. fabula, are both plentiful in Kames Bay, but their range is not coincident.

Eipe sperms were found from May onwards and ova were rounding off in June.

Young Tellina tenuis, passing the 2-mm. sieve but retained by the 1-mm. sieve, were found in Kames Bay in August, chiefly below L.W.M., but in October plentifully distributed up to half-tide and in lesser numbers higher up the shore.

The food usually consists of vegetable detritus, but during the spring increase diatoms appear almost exclusively in the gut.

The nomenclature followed is that used by Hartmeyer (9), in which account will be found identificattion keys and complete lists of the synonymous species, only the commoner of which are given below. That his conclusions in this respect are open to question has already been pointed out (see Journ. Mar. Biol. Assoc., Vol. XV, p. 159).

For a description with figure of a species the reference number is placed after the name.

1. Observations made subsequent to December, 1925, confirm the conclusion that the nitrates in the water of the English Channel, twenty-two miles south-west of Plymouth, are almost entirely utilised by phytoplankton in the summer, and are reformed in early autumn at a greater rate than they are utilised.

2. Movements of the water masses are shown to affect the quantity of nutrient salts available for phytoplankton in the waters immediately north of Ushant.

3. The effect of land drainage on the quantity of nitrate in the sea is not apparent beyond a few miles to seaward from Plymouth Sound, being masked by the nitrate which is regenerated from dead marine organisms.

4. The nitrate in the river and estuarine waters entering Plymouth Sound is nearly all utilised by plants in the rivers and estuaries themselves before reaching the open sea during summer.

1. A comparison of the strength of the wind, Beaufort Scale, and of its direction during the periods when the vernal diatom outburst caused phosphate depletion of the surface water, has failed to indicate that there is any connection between either strength or direction and the date of the outburst. The spring sunshine still appears to be the important factor at El.

2. The sequence of the years studied as regards the main spring diatom outburst deduced from phosphate depletion at Station El is as follows: 1924, early March; 1926, late March to early April; 1925, early April; 1923, early May.

In the whiting, no significant changes occur in the composition of the muscle substance, either throughout the year, or with increasing age, or during ripening of the gonads.

The amount of fat in the liver is very low in immature fishes, increasing greatly with age, and reaching its maximum just after the commencement of the ripening of the gonads. It then falls off, reaching its lowest value amongst mature fishes in the “Spent” stages. Males are richer in liver fat than females.

Immature fish have a decidedly higher protein content in the liver than have mature fish.

1. Under the conditions of the tests cotton and hemp nets became rotten in Aquarium tank water in two months or less in summer, in 4½–5½ months in winter.

2. A mixed copper soap, containing oleate, stearate, and palmitate, is as good, probably rather better, than is copper oleate as a net preservative.

3. “Cuprinol,” a petroleum acid copper soap, is better than the fatty acid soaps, both in fresh and in salt water. It is more than three times as expensive, however.

Towards the end of the year 1924, the present writer commenced a statistical study of random samples from commercial landings of herrings at Plymouth, in order to obtain information on the two following questions:—

(a) Upon what year-class or year-classes of herring was the season's fishery of 1924–25 concentrated?

(b) Did the fishes landed throughout that season appear to conform to a single morphological type?