A local race of Idotea viridis from south-east Essex is described and its classification as /. viridis discussed. This animal is a nektonic form and so far has only been found in New England Creek in south-east Essex. The biology and post-embryonic development of this race is described. Quantitative samples were taken of the animals present in the creek in 1934, 1935 and 1936. I. viridis was rare in the first five months of the year; numbers rose to a maximum in late June and July and remained comparatively high until the end of October.

The number of young in the brood pouch is very variable. There is some evidence that the number of fertilized eggs was reduced by the expulsion of embryos before their development was complete. The newly hatched I viridisis described.

A study made of the adaptations to tubicolous life found in the small brackish water Photid Amphipod, Leptocheirus pilosus Zaddach, revealed several interesting points.

The presence of cement glands in many amphipods has been recognized by several previous authors. In L. pilosus these glands are found mainly in the upper joints of the first two pairs of peraeopods, opening to the exterior through a common duct in the claw. Unicellular glands are also found all over the body, particularly on the coxal plates.

The copepods described in this paper come from two sources, the Firth of Clyde and the St Lawrence River. Several new species were collected from Balloch Bay on the Greater Cumbrae in 1935 and 1936 during an attempt to obtain some of the early species described from Scottish waters. The remainder were collected while working at the Biological Station at Trois Pistoles, Quebec, during a visit to Canada in 1937. The environment in Balloch Bay is composed of a fine muddy sand, strewn with boulders. The bay is on the eastern side of the island and therefore in a sheltered position. A description is given in Appendix III of The Biology of the Sea Shore, by Flattely & Walton (1922). The conditions under which the Canadian material was found will be dealt with in a later paper describing the remainder of the collection from the St Lawrence; it will be sufficient here to state that the conditions are essentially marine.

Copepods from three allied genera are included here: Paramesochra T. Scott, 1892; Leptopsyllus T. Scott, 1894; and Remanea Klie, 1929. The first two have for some time been in a state of considerable confusion and it has been a matter of some doubt into which genus the various species should be placed. Several efforts have been made to clarify the position (notably by Klie, 1929 and Monard, 1935) but the more recent work of Kunz (1938) has produced a clear separation based on the presence or absence of an endopod on the second leg.

Although the medusa Dipurena halterata (Forbes, 1846) is well known, and has been figured by a number of authors (e.g. Forbes, 1848; Browne, 1897), the hydroid of this peculiar species has remained unknown. This medusa is rather scarce at Plymouth (Russell, 1938). On May 3 1938 I had the good fortune to find at Plymouth a small hydroid of the Syncoryne type which later liberated young medusae, and these proved to be young specimens of Dipurena halterata.

The nematocysts of the three species of Leptomedusae, Aequorea forskalea, A. vitrina, and A. pensilis, and of the two siphonophores Agalma elegans and Velella velella are described.

The specific characters of the three species of Aequorea are discussed and it is shown that A. pensilis is probably the same species as A. macrodactyla

In the flounder adipose tissue forms a padding between the muscles to the dorsal and ventral fins. A little is present under the skin, more especially where the lateral line septa and the myocommata meet the skin. In addition a quantity of fat is associated with the skeleton.

Immature flounders living in the estuaries of the Tamar and Lynher are fattest after intense feeding during the summer, and leanest after the winter fast.

Maturing flounders have a high fat content before going to sea to spawn. While in the sea during the spawning season, February to April, very little feeding takes place and there is a rapid drop in fat content. Spent fish are very lean.

Those females which return to the estuaries after spawning rapidly make good their fat loss.

The present report continues the series of observations on the seasonal abundance of the pelagic young of teleostean fish in the plankton off Plymouth (Russell, 1938b), and gives the results for the year 1938. These results are published in the same form as in previous reports. The dates on which collections were made with the 2 m. stramin ringtrawl are given in Table I, and the monthly average catches of the young fish per half-hour oblique haul in Table II.

Analyses of phosphorus, nitrogen, iron and manganese are recorded for Balanus nauplii (a cirripede crustacean), post-larval Callionymus (a teleostean fish), mature Sagitta elegans (a chaetognath), Pleurobrachia (a ctenophore) and for crab zoeas and megalopas (Table I). A sample of Sagitta setosa in 1934 contained much more iron than that in S. elegans here reported. The ctenophore, Pleurobrachta, is relatively poor in phosphorus, nitrogen and iron and its ash-free protoplasm must evidently be rich in either fats or carbohydrates. Neither Pleurobrachia nor Balanus nauplii effect any appreciable concentration of manganese from sea water.

New values for the extinction coefficient of red light in distilled water require that published results for this coefficient in waters from the Tamar Estuary shall be increased by o.1, 1.3 and 2.0 at 610, 720 and 750 mμ respectively. Earlier deductions as to the favourable transmission of red light in turbid estuarine waters apply only up to about 680 mμ. That part of the extinction coefficient due to suspensoids and colouring matter was inversely proportional to the first power of the wave-length. Other conclusions remain unaffected.

The plankton collected at a station in the Bristol Channel in 1936-7 is related to chemical and hydrographical factors.

On account of the varying speeds of the tidal streams, the observations refer, not to a single point, but to a series of points along a length of the channel. Gradients of salinity, phosphate, and a possible complicated gradient of oxygen saturation, were determined, and, from the average monthly salinities, an annual cyclical movement of water deduced.

Two groups of young herring are found in the Clyde. One, the offshore group, has been identified as Clyde spring-spawned herring; the other, the inshore type, is of unknown origin. The former were caught only occasionally, the latter at fairly regular intervals during their first year.

The two groups are distinguished by differences in size and identified as belonging to different races by vertebral counts. There was no intermixture.

The offshore herring which metamorphosed at the end of May when 40-50 mm. long, reached a length of 90-100 mm. in winter. The inshore fish which were about 50 mm. long in May reached a length of about 130 mm. in winter.

The swimming and burrowing habits of four species of the genus Bathyporeia have been examined and shown to be alike, and similar to B. robertsoni as described by Schellenberg.

Swimming is effected by the pleopods working in a metachronal rhythm, drawing water along a ventral groove formed by the coxal plates of the second peraeopods and the expanded bases of peraeopods 3, 4 and 5.

The main water current enters anteriorly between the second gnathopods and is filtered by a series of feathered bristles borne on the basis of this appendage; a subsidiary current enters between the second and third peraeopods.

Burrowing is effected mainly by the sweeping action of the second gnathopods and first two pairs of peraeopods, aided by the first and second uropods as soon as they can obtain a purchase on the sand. The adaptation of these three pairs of appendages to burrowing is explained.

The zonation of four species of the genus Bathyporeia, from high-water mark to low-water mark, in Kames Bay, Millport is given. B. pilosa occurs above the high-water mark of neap tides, B. pelagica is a mid-tidal form and B. elegans a low-water form. The latter, together with B. guilliamsoniana, extend beyond low-water mark. Of the population, as it occurs in the sand, 15 % are adult males, 26 % adult females, giving a proportion of adult to immature forms of 4 1 : 59.

The analysis of forty-five tow-net samples taken across the bay at night shows that the same zonation of the species is maintained; the proportion of adults to immature forms in these samples, however, is as 57: 43, and of the 57 % of adults, 42 % are adult males, 15 % adult females.

When the samples are related to the day of the lunar month it is shown that the numbers increase in the tidal waters in the periods immediately preceding the full moon and preceding and partly overlapping the new moon. A nocturnal vertical movement appears to be a marked feature of a few benthic amphipdd families, but the factors which cause this migration are problematical and require much further investigation.

The description of the material used in the present investigation does not conform with that of Horstadius. Attention is drawn to this lack of agreement. A hypothesis based on viscosity changes within the egg has been advanced to explain the rounding off of eggs in sea water.

By means of what is called the transfer series the egg batch has been divided into a number of parts; the last liberated eggs being the ripest. The occurrence of large numbers of egg batches giving low maturity values has been attributed to maturity resulting from a series of changes whose rate after initiation gradually increases.

Attention is drawn to seasonal changes in the reactions of the germinal products. No definite lunar periodicity is shown in the ripening of the eggs.

The diatom Ditylum brightwelli requires, for vigorous growth in artificial sea water, two organic substances, or groups of substances, in addition to inorganic salts. The substances, or groups, act in a manner complementary to each other.

The effect of adding either is greatly increased by the presence of the other.

One accessory substance, or group, has been obtained in impure state from natural sea water and from extracts of algae by adsorption on carbon and elution. It has properties of an inorganic acid or internal anhydride.

Chthamalus stellatus is a littoral barnacle very similar in habitat and general ecological relations to another littoral barnacle, Balanus balanoides. In those localities where both species flourish they compete considerably for space, and also possibly for food. The fact that B. balanoides settles sooner after the winter storms than does Chthamalus probably favours the former.

Chthamalus is characteristically a southern species and Balanus balanoides a northern one, but the north and south ranges of the two species overlap in the British Isles and in France. The determining factor is presumably temperature.

Chthamalus is an Atlantic species, and Balanus balanoides is more characteristically a North Sea species. The essential factor in Atlantic water remains unknown, although in respect of a need for Atlantic water Chthamalus resembles Sagitta elegans and intertidal Echinus esculent.

The new species of Gammarus here described was first noted in 1931 by Prof. H. Munro Fox, to whom I am indebted for the opportunity of examining it. He found it in abundance in the Droitwich district, living in the brackish waters of the River Salwarpe near the town, in the Canal, and in Wyken Slough near Coventry.

An account of the chief earlier experiments, from those of Cavolini in 1785 to the close of Moores experiments in Florida in 1905, is given and the general subject of reconstruction and growth in the sponge cutting is described in detail.

Under favourable conditions loss of volume in the initial stages, following cutting, should be practically negligible, the early steps in repair and reconstruction proceeding without delay after severance of the fragment from the original sponge. As chief among these, the dermal covering required for newly cut surfaces, the closing of most of the exposed apertures of the old canal system, and the retention of one or more of these for future oscula, are accomplished rapidly and, for preliminary purposes, are completed within a very few days