The Saltash tuck-net is used in the estuaries of the Tamar and Lynher for seine netting on soft mud. The fishery is carried on during autumn and winter, from open boats with crews of two men.

Hauls were made with a tuck-net in every month between November 1935 and December 1937.

The fish population of the estuaries is essentially marine: its composition changes from month to month with the arrival from, or departure to, the sea of different species of fish. With the exceptions of salmon (Salmo salar), sea trout (Salmo trutta) and some of the Gobiidae, all the fishes of the estuaries go down to the sea to spawn.

Buoys differ from the intertidal area in that they are constantly immersed near the surface of the water and the slope and texture of their surface is constant. The horizontal and vertical distribution of the macrofauna and macroflora on a series of buoys stretching from the open sea up the Tamar estuary is given.

There are differences in estuarine penetration even among species belonging to the same genus. Distribution is likely to be affected by the time of laying the buoys and the period in the water. But the six buoys farthest from the sea were laid down and lifted at approximately the same time. For these, at least thirty species were available for colonization, but little more than half that number was found even on the most seaward; and the number decreased up-river.

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.

Light-adapted mysids as exemplified by Hemimysis lamornae display phototelotaxis which regularly alternates in sign from positive to negative and vice versa. This reaction may be disturbed by other activities such as feeding; it only takes place in horizontal illumination.

Dark-adapted mysids display negative geotaxis. When a light stimulus is given this geotaxis is reversed in sign irrespective of the direction of the incident light.

When the statocysts of the mysids are removed their responses are much more like those of planktonic creatures. In the light normal orientation is maintained by the “dorsal light reflex”, and in darkness by the “general position reflex”. In the darkness a feeble negative geotaxis is sometimes seen. In light, phototaxis is seen in both light-adapted and dark-adapted conditions; in the majority of cases it is negative but on occasion has been seen to be positive.

In 1932 crosses were made at Plymouth between Psammechinus miliaris ♀, both Z-type (from the shore) and S-type (from Eddystone), and Echinus esculentus ♂. The larvae from the S eggs differed in size and shape from those from the Z eggs (cf. Figs. 1,2 with 3–6). None of the hybrid plutei possessed the green pigment of P. miliaris, nor the posterior epaulettes of E. esculentus. Some of the larvae (Figs. 3, 4) had a posterior pedicellaria, like E. esculentus, in others this organ was missing (Figs. 1, 2, 5, 6). Some of these plutei were preserved, others went through metamorphosis. Healthy larvae of these combinations (00+ and 000) have not hitherto been described. The results are compared with those of previous authors (see table, p. 100). Some possible causes of change of inheritance in different years are discussed.

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.

A method is described for obtaining growths of phytoplankton in samples of crude sea water, similar in composition but several hundred times more dense than phytoplankton communities occurring in the sea.

The ratio of nitrogen to phosphorus utilized by such communities has been determined.

They use ammonium in preference to nitrate, although the latter may be many times more concentrated than the former.

They use urea and uric acid as sources of nitrogen.

Certain amino-acids when added as sources of nitrogen were attacked by the bacteria in the community and either the ammonium set free or both the ammonium and the amino-acid were used by the phytoplankton. Others, as d-leucine, were not utilized, or, as l-leucine, only slowly utilized.

Sodium nucleinate and caseinate were rapidly broken down when added to crude sea water by bacterial action, and the phosphate produced utilized by phytoplankton. There was no significant utilization of glycerophosphate.

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.

The amount of iron and phosphorus in Sagitta setosa and S. elegans has been estimated. As the winter population decreased in numbers the iron content per animal also decreased, rising again in what may have been the next brood.

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.

This paper gives an account of a survey of the invertebrate populations (omitting Protozoa) of eight species of seaweeds on Church Reef, Wembury Bay, extending over the entire intertidal range.

Above high-water neaps the faunas are poor, except for that in Lichina pygmaea which is the richest in individuals on the shore.

Between high-water neaps and low-water springs the most numerous groups are copepods, acarines, young littorinids and (in Ascophyllum only) ostracods.

In the holdfasts of Laminaria digitata polychaetes are very abundant and make up the majority of the population.

The intertidal faunas are compared with those in the soil on land, and prove to be far more abundant. Even the most plentiful group in the soil, the insects, is rarely as numerous as it is in Ascophyllum around mean sea-level.

Altogether 177 species are recorded, of which 35 are not in the Plymouth Marine Fauna (1931).

Ten stations, from high water to low water, were investigated along a mud-flat in the Bristol Channel.

The mud was analysed for water content and grade. The values suggested, with other observations, that the stations were distributed over two different areas.

Quantitative analysis of both macrofauna and microfauna revealed a dense mud population.

The operative ecological factors, including the food cycle, are defined.

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.

It has long been presumed that the gametes of certain Foraminifera are flagellated; however, the lack of conclusive evidence as to the origin and fate of these flagellated gametes has made their existence problematical.

In syzygous species of Discorbis the gametes are flagellated and the genetic relationship of these gametes is easily demonstrated, since gametogenesis, fertilization, and the development of two- and three-chambered multinucleate microspheric agamonts takes place within the excavated tests of two or more mononucleate megalospheric gamonts associated in syzygy.

The life cycle of Discorbis herein described is in general agreement with the life cycle of Polystomella crispa proposed by J. J. Lister, and completes an interesting series of life cycles in which a progressive modification in behaviour and test morphology can be traced.

Behaviour, ecology, and distribution of four syzygous species of Discorbis are discussed.

Multiple tests of these syzygous species of Foraminifera can be found in most rock-bottomed tide pools that supports a growth of coralline algae. These sexual groups provide a sure source of material for the demonstration of flagellated gametes in the Foraminifera.

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.

The survey, the results of which are described in this paper, was primarily intended to investigate the zonation of Littorina littorea, but notes have also been included of the zonation of such other gastropod species as occurred with it. The material was collected from the following localities: Torpoint. 2. ×. 36. Just west of the ballast dock at Torpoint, Cornwall. The shore consists of stones, many of them bedded in mud, and thickly overgrown with fucoids. There is little wave-action, but at times a considerable drop in salinity (Hartley & Spooner, 1938; Mime, 1938).