A quantitative seasonal survey of the phytoplankton and small zooplankton has been made from the end of January to the end of August 1939, at a station, L4, with supplementary observations at a station off Rame Head, both near Plymouth. The results are compared with those of a fuller survey made in 1934.

The spring maximum in numbers of plant cells was late, not being reached until the middle of April.

The monthly means of the total numbers of animals caught were of the same order in the two years, but the numbers of copepods plus copepodites in 1939 were only two-thirds of those in 1934.

The process of moulting in Pseudoprotella phasma is described. Sixteen instars have been found with a discontinuity in growth at the third stage. The instar lengths differ by a common ratio of 1·169 in the male and 1·148 in the female, the animals becoming differentiated at the twelfth stage. There are no secondary sexual characteristics except the brood pouch. The growing parts display simple positive allometry. The growth rates of the chelae and antennae alter after stage XII but remain the same in the third body segment. Changes in shape in the chelae, antennae and spinous armature are described.

On June 15 and 20, 1938 Mr W. J. Rees of the laboratory of the Marine Biological Association, Plymouth, collected some mud samples at Mewstone and Rame Mud near Plymouth for Mr J. Hult, Uppsala. By kind permission of the director of the laboratory and of Mr Hult I have examined the Ostracoda contained in the samples.

The general larval characters of the genus Spirontocaris are summarized by Gurney (1937b), but since his paper was written there have been published descriptions of S. spinus var. lilljeborgi (see Lebour, 1937) and of S. pusiola (see Bull, 1938). The four British Columbian species described by Needler (1933) must also be taken into consideration. With our present knowledge of all these species the description must be slightly modified. We now know the larvae of all the British species of this genus with the exception of the typical form of S. spinus. The specimen from which the larvae were hatched was intermediate between the typical S. spinus and the var. lilljeborgi and was regarded as the latter. The following species are British: S. polaris, S. spinus and its var. lilljeborgi, S. gaimardi, S. pusiola, S. occulta and S. cranchi. S. polaris is a northern form, the only British records being from the Shetlands. It has an abbreviated development, described by Stephensen (1912b, 1916, 1935).

The nematocysts of five species of Anthomedusae, six species of Leptomedusae, and one Trachymedusa are described.

In view of the additional support supplied by characters of its nematocysts it is suggested that the genus Chromatonema should be placed with Tiaranna in a new family, the Tiarannidae, in the Anthomedusae.

Evidence on the possible evolution of microbasic euryteles from stenoteles is afforded by the nematocysts of Aglantha.

It is generally assumed that there are two species of the genus Podocoryne, in northern waters, in which free swimming medusae are produced, P. carnea M. Sars and P. areolata Alder. Of these, the hydroid of P. carnea is known for certain, and that of P. areolata is thought to be the hydroid described by Alder under that specific name. Recently, I have found that there are two more species of Podocoryne medusae in British waters, P. hartlaubi Neppi & Stiasny and P. minima (Trinci). There are, therefore, two more hydroids to be found and it will be shown that the identity of the hydroid of the so-called medusa P. areolata must remain in doubt.

Several specimens of an ichthyobdellid leech were found on Blennius pholis collected on the coast of Anglesey.

The leech resembles Abranchus sexoculatus (Malm), a rare form only recorded previously from Sweden and not yet adequately described. Slight differences, however, indicate that it may be a distinct species and the name Abranchus blennii is provisionally put forward for it.

A short review of the genus Abranchus and a description of the appearance and structure of the leech follow.

My thanks are due to Prof. F. W. Rogers Brambell for his encouragement and advice; and to Mr W. H. Leigh-Sharpe for advice regarding the literature.

The following paper is a record of certain work which was carried out at the River Yealm during 1939. No claim is made for original work, but it may serve some useful purpose as a record.

Oysters from die River Yealm have been used in most of the experimental work carried out on the breeding of oysters at Conway. But, for some unknown reason, there has never been any relevant growth of native oysters in the Yealm. The beds are stocked every year with three-year-old Brittany oysters. These oysters thrive well in the Yealm and are of considerable commercial value.

Certain old tanks at the Fisheries have been altered and repaired for the purpose of cleansing prior to their despatch to die London market. These tanks are in use for this purpose approximately from the end of August until die beginning of May. Therefore they are unused for approximately four mondis during die breeding season.

The habitat, external appearance and habits of members of the Erycinidae, Montacutidae and Galeommatidae, three families included in the order Leptonacea, have been investigated and are described.

The ciliary currents of the gills, palps, visceral mass, foot and mantle are described in detail.

There is some reduction in the shell in this order. In Kellia, Lasaea, Montacuta and Mysella the shell is external and the adductor muscles are well developed. In Galeomma the shell and adductors are reduced, and in Devonia the shell is also partially covered by the mantle.

The foot is modified, and all members of this order progress on the flattened ventral surface of the foot which forms a creeping sole. The burrowing habit is lost.

This paper presents results of an ecological study towards high-tide level near the mouth of the Dovey estuary, carried out in 1925–6. The area was treated as an extension of the sea floor, the only comparable work at that time being submarine. Petersen (1918) showed that on the bed of shallow seas the fauna could be grouped into “animal communities”, whose constitution was determined by depth, distance from shore, shelter and salinity. Analysed with regard to distance from high-water mark, and degree of shelter, the fauna of this part of the estuary shows Petersen's Macoma community over most of the area, with a Corophium community at high tide in the more sheltered part. Davis (1925), in the North Sea, substituted “soil associations” as an alternative ecological unit, a certain grade of soil carrying its typical fauna wherever it might be found. The two groupings already found in the Dovey estuary clearly emerged as soil associations, after adoption of a reliable method for analysis of fine-grade soils. Up to the present, oceanographers have used sieves or elutriation for soil analysis. Up to the present, oceanographers have used sieves or elutriation for soil analysis. These methods are unsatisfactory for examinations of estuarine soils, with their large proportion of fine material.

The advantage of using laboratory-reared animals in the elucidation of trematode life histories is now generally recognized (Palombi, 1938; Stunkard, 1938, etc.). Further researches seem to emphasize this point. No matter how carefully controls are examined and no matter how precise is the morphological comparison between cercaria, metacercaria and adult fluke, the fact that the intermediate and final hosts have been exposed to previous infection in the wild—particularly by closely related species of worms—immediately detracts from the value of the experiments.

The number of eggs produced by the herrings of the East Anglian shoals increases with the length of the fish at a rate equal to the 3·465 power of the length, and with the age of the fish to the 0·66 power of the age. This fecundity is compared with that found in other races of herrings.

The number of eggs produced is closely correlated with the mean weight of the ovary, and it is found that the weight of the ovary increases with length at a rate equal to the fourth power of the length, and that a slightly higher rate applies to the testis.

The weight of the gutted fish, however, increases in relation to the length at a much slower rate, namely, as the 2·3 power of the length in the males, and the 1·5 power of the length in the females.

The genus Gammarus, instituted by Fabricius in 1775, has come to include a large number of species—so many and so varied, in fact, that the necessity for a revision of the genus is well recognized. An extensive examination of the taxonomic literature has inevitably led to the conclusion that several more or less well-defined groups of species can be recognized among the total assemblage, and that some of these at least should be separated off as distinct genera.