The accuracy of volume estimation in filling a marked tank by means of a plankton pump has been determined. The method even in its simplest form is satisfactory under good conditions. Further refinements, in which the plankton was filtered off, after filling a modified tank (for example with an overflow device) would no doubt increase the accuracy.

A device is described by which, using an ex-N.F.S. pump, a constant (but variable by selection) volume of water can be taken without the use of large tanks.

A small number of sets of samples taken with adequate volume control indicate the same order of variability as net hauls. Comparison of the distribution of x2 for paired samples with nets and pumps also indicates variation of a similar type.

These results suggest that the variability of net hauls is not entirely due to the variations in the volume of water filtered. Further work is in hand to elucidate this question.

Nauplii of the first two stages were obtained from adult Elminius modestus and larvae of all stages, except the smallest, were obtained from the plankton over Essex oyster beds.

Over 200 nauplii of all sizes were measured. Their size distribution, plotted graphically, showed six peaks corresponding to six naupliar stages. The later stages were much more variable in size than the earlier stages.

The size limits and characteristics of each naupliar stage are given. Briefly, Stage I has the fronto-lateral horns pointing backwards. Stage II has the caudal spine much longer than the abdominal process. Stage III has the abdominal process about as long as the caudal spine, but has no carapace fold posteriorly. Stage IV has a carapace fold but no sign of the abdominal appendages. Stage V has the rudiments of these appendages showing indistinctly within the abdomen. In Stage VI the abdominal appendages are prominent.

Considerable differences were found in the size compositions of populations of Asterias rubens off Plymouth. These differences were not correlated with age.

Laboratory observations on rate of growth showed that well fed starfishes grow fast during summer and autumn and somewhat slower in winter. Poorly fed starfishes did not increase in size, but were able to survive for long periods with a minimum of food.

It is often desired to grow animals and plants of the intertidal zone in the laboratory, under conditions as far as possible simulating those in nature and with the least trouble and expense. This need was felt by the writer during an ecological study of the diatoms inhabiting the mud-flats at Whitstable, Kent. It was found necessary to maintain such diatoms in the laboratory in London in a healthy condition for several days so as to study the effect of light and tides on their movements. The apparatus described in this paper was therefore devised. It has an advantage over other tidal systems (Bracher, 1919; Martin & Reid, 1935) in that the substratum could be automatically alternately flooded and drained at regular intervals by a much simpler mechanism. Besides, it is more handy and can be operated with only a small supply of sea water, a matter of some importance in localities remote from the sea.

It consists of a tidal chamber, T, and a reservoir, R (Fig. I). The former is an inverted bell-jar fitted with a rubber bung through which passes a long glass tube, g, which extends to the base of the reservoir. At the upper end of the tube is a small funnel by which sea water enters the apparatus. A ⋯tube, t, serves to connect the tidal chamber and reservoir, its horizontal arm being connected to the siphon S.

The wide-mouthed bottle constituting the reservoir is fitted with a stopcock, v, which is useful for expelling air when setting up the apparatus.

The first larva of Typton spongicola was described in 1925 from the eggs carried by the parent (Lebour, 1925). No later stages are known; therefore it was interesting to find a last larva in the plankton from 2 miles north-east of the Eddystone (21 August 1946), which changed to the post-larva in the laboratory. There seems to be no doubt that the identification is correct although, surprisingly, the antennal scale, rudimentary in the adult, is still large. The agreement in colour of the last larva and post-larva with the newly hatched first larva, and the great similarity in the structure, in most ways, of post-larva and adult, makes it practically certain that we are dealing with T. spongicola.

The analysis of data on replicate vertical plankton hauls gives a value of the order of 35 % for the coefficient of variation of a single observation for a haul of moderate length. The results are similar to those presented by Winsor & Walford (1936), and Winsor & Clarke (1940); and are not at variance with the suggestion that the animals are randomly distributed, and that the variations obtained are largely dependent upon variation in the volume of water filtered by the net.

Erosion of Dawlish Warren, at the mouth of the Exe Estuary has resulted in a redistribution of sand, which has come to lie in close proximity to certain of the original mud banks.

Quantitative collections of the macrofauna were made along a traverse passing from the newly deposited sand to the old mud bank, stations all being at about half-tide level.

Measurements of salinity, temperature, pH, currents and wave action show that these are similar for all stations. Thus it has been possible to observe the distribution of the fauna in relation to the type of soil without the usual complications due to differences in other factors.

The worms were housed in glass U-tubes, and were able to get a supply of aerated water from above by making pumping movements. The water movements were recorded kymographically. The experiments generally lasted for 24 hr. or longer.

Six species of rotifer, including one oceanic species and representing four genera, are recorded for the first time from Plymouth. Remarks are made on various interesting features of their anatomy, details are given of their times of occurrence at Plymouth, with notes on their location and known distribution in other parts of the British Isles, and in foreign waters.

Attention is called to the apparent poverty of the Plymouth marine and brackish-water Rotifera as compared with that of Liverpool, investigated at length by Galliford. It is stressed that no exact conclusions as to the reason for this can be made until after a more exhaustive survey, as some likely habitats adjacent to the Sound were not investigated. Attention is also called to the caution which must be exercised in terming rotifers marine, as most of those collected in coastal waters appear at present to be confined to areas where a considerable amount of fresh water is discharged into the sea. At least two species, one of which occurs in the Sound in May, are known to be truly oceanic, having been found in mid-Atlantic.

It is suggested that ‘brackish’ and ‘estuarine’ are the terms most applicable to the majority of coastal rotifers in the present state of our knowledge.

Monthly samples of the Laminariaceae, L. saccharina and L. cloustoni, from three localities on the Argyllshire coast have been taken from March 1948 to March 1949, and analysed for dry matter, ash, mannitol, laminarin, crude proteins, inorganic nitrogen and alginic acid, and the seasonal variation in these constituents correlated with the changes in composition of the sea water.

The results show that a correlation does exist and that a period of rapid photosynthesis occurs from March to June/July, but is restricted in July/August when nitrate is undetectable in the water and phosphate is as low as 0·16–0–20 mg. atom/m.3. The replenishment of the photosynthetic layer with nutrients is retarded in July/August, apparently due to the warming of the inshore waters, which may set up a thermocline restricting vertical mixing.

The autumn cooling of the uppermost waters facilitates vertical mixing, regenerating the nutrients in the photosynthetic region, and a second burst of photosynthesis at a reduced rate from the spring ‘outburst’ occurs in October/November.

The results of phosphate determinations in sea water by the Deniges method, using red light, in an absorptiometer, may be in error if the stannous chloride reagent has low HC1 concentration, and contains stannic tin.

The error is in the reagent blank determination, and seems to be caused by colloidal stannic compounds which increase the opacity of the solution. In sea water the effect may be smaller or immeasurable so that results are over-corrected.

When the stannous chloride solution contains about 5% hydrochloric acid, reagent blank figures are low, and independent of stannic tin concentration. This acidity is recommended.

Worms were allowed to burrow in sand in the laboratory. The general form of their burrows resembled that found in the field. Their behaviour was studied by continuously recording the water movements through the burrows for periods up to 3 weeks.

Whenever the worms were feeding from a gradually subsiding cone and piling up castings, as they do in the field, a characteristic cyclical pattern was traced. This was marked by conspicuous diphasic excursions at intervals of about 40 min. Defaecation occurs at the summit of the first phase. By comparison with records got from worms in glass tubes (Wells, 1949), it is inferred that the first phase consists of tailward locomotion to the sand surface, and the second to headward irrigation accompanied by gentle creeping back to the feeding point. The whole cycle is identical with the intermittent irrigation cycle shown in glass tubes.

Six marine flagellates, used as food in the rearing of the larvae of Ostrea edulis L., are described.

One belongs to the Chlorophyceae, Pyramimonas grossii n.sp. (Polyblepharidaceae); four belong to the Chrysophyceae, Chromulina pleiades n.sp. (Chromulinaceae), Isochrysis galbana n.g., n.sp., Dicrateria inornata n.g., n.sp., D. gilva n.g., n.sp. (Isochrysidaceae); and one belongs to the Cryptophyceae, Hemiselmis rufescens n.g., n.sp. (Nephroselmidaceae).

A form of reproduction in a palmelloid phase, not previously described, is recorded for the Isochrysidaceae.

In July 1938 I succeeded in rearing the hydroid of Eutima gracilis (Forbes and Goodsir) (also known as Saphenia gracilis) from adult medusae which liberated their eggs and sperm in finger-bowls of sea water. These hydroids were only in the primary polyp stage, and I withheld publication hoping to repeat the work later and perhaps rear the hydroid to a more advanced stage. As it is unlikely that I may now have the opportunity of doing this it seems worth while to publish a short account with figures of the polyp.

The post-larval sand-eels (Ammodytidae) occurring in the Celtic Sea and Plymouth area are identifiable as Ammodytes lanceolatus, A. tobianus, A. marinus (not previously recorded from the area), and a fourth species of Ammodytes, the adult of which, it is concluded, is not yet known.

Adult Gymnammodytes semisquamatus (not previously recorded from the Plymouth area), the young of which are not yet known, increases the number of species in the area to five.

Records of the young fish and plankton of Plymouth off-shore waters taken in ½ hr. oblique hauls of the 2 m. stramin ring-trawl were continued in 1948. They show an even lower production of young fish than in 1947 and a continued poverty of plankton organisms other than young fish. The dates on which collections were made are given in Table I.

The method described below was evolved as a substitute for counting, which is unsatisfactory for epiphytic marine diatoms. It depends upon the estimation of the amount of diatom-silica associated with unit dry weight of the sub-stratum. The sea-weed samples are first freed from sand particles and are then treated with strong nitric acid in the usual way. In order to convert the insoluble silica of the diatoms into a soluble form suitable for chemical estimation, the material is fused in a platinum crucible with a mixture of K2CO3 and Na2CO3 and the fused mass is dissolved in (silica-free) distilled water and filtered. The amount of silica in the filtrate is determined colorimetrically according to the method of Dienért and Wandenbulcke (cf. Atkins, 1926). The method is simple in practice and saves considerable time and labour. The full procedure is illustrated by reference to a study of the periodicity of Grammatophora marina (Lyngb.) Kütz. at Swanage, Dorset.

This species (PL. I) is found all the year round on Cladophora rupestris in a pit in one of the reefs at Peverel Point, Swanage. In summer it is the only epiphytic diatom on the Cladophora, while in spring and autumn small numbers of other epiphytes (Cocconeis, Opephora, Rhoicosphenia) are present. In order to obtain a fairly representative picture of the abundance of Grammatophora at different times, samples of the Cladophora were collected monthly from a definite area in the pit, each including 3–4 cm. of the apices of five to ten Cladophora tufts cut at random.

The evidence points strongly to the effect that Sheringham fishes the same race of lobsters as ports farther north. The most likely explanation of the smaller average size of the lobsters at Sheringham, which is shown to be due to abundance of small and rarity of large, is that it is in some way natural, and not due to fishing. A neat theory to fit the facts is Meek's, based on the position of Sheringham downstream in the main current system.