Experiments on yolk utilization were done with developing herring eggs and larvae from races spawning in the Clyde, North Sea, Atlantic and Baltic. The range of mean dry weight of unfertilized eggs varied from o·126 to o·366 mg in the different races.

The ultra-structure of the epidermis of herring larvae is described. It is composed of two cell layers; the outer layer contains mitochondria, vesicles and a practically continuous layer having a dense 'fibrous' appearance. The cell border in contact with the sea water is thrown into an irregular arrangement of ridges and pits. The inner cell layer is usually thicker than the outer layer and lacks the continuous dense layer. No differences could be found in the structure or thickness of the epidermal cells of larvae reared in salinities of 5, 17·5, 35 and 50 ‰

It has not been known with certainty that the haddock produces underwater sounds of biological significance, though various authors have suggested the possibility.

Descriptions are given of sounds (grunts and rasp-like noises) produced in particular behavioural contexts by haddock maintained in tanks, and of sounds recorded at sea and attributed to haddock. Oscillograms and a spectrogram of these sounds are given. It is suggested that the sounds are involved in aggression and self-defence.

The sound-producing mechanism is described.

The eggs of two common cirripedes, Balanus balanoides and B. balanus, have been analysed at different stages of development for their lipid content.

Triglyceride and phospholipid are the main lipid components; small amounts of free fatty acids, lipochromes, sterols, and some very non-polar material (possibly hydrocarbon) are also present.

Lecithin followed by phosphatidyl ethanolamine make up a large proportion of the phospholipid fraction.

The fatty-acid spectrum is similar to that of other marine animals being rich in unsaturated fatty acids of which eicosapentaenoic (20:5) and docosahexaenoic (22:6) predominate.

Triglyceride is lost during development.

Initially some lecithin and phosphatidyl ethanolamine are lost during development, but they accumulate in the late stages.

Cardiolipin shows a marked increase in quantity during the late stages; this is presumably associated with increased cellular differentiation.

There is a tendency for all the components to approach the values for the adult bodies—taken when lipid reserves are minimal—as the embryos develop.

Data are presented on the lipid composition of Balanus balanus spermatozoa.

Lecithin is the major lipid and little plasmalogen is present.

The results are discussed in relation to what is known of other spermatozoa, both vertebrate and invertebrate.

Some data on the inorganic and organic constituents of Balanus balanus seminal plasma have been given by Barnes (1962 a, 1963); lipids were shown to be present in the plasma and are a well-known constituent of the spermatozoa of other animals (Mann, 1964). In view of the relatively small amount of data on the detailed phospholipid composition of invertebrate spermatozoa the opportunity was taken during the investigation reported in the previous paper (Dawson & Barnes, 1966) to examine the spermatozoa of Balanus balanus. The results are, however, best presented and discussed separately. The results are given in Table 1.

The definition of Ectocarpus by Hamel (1931–39) is accepted and his division of the genus into two species complexes, E. fasciculati and E. siliculosi, vindicated. Observations on the E. fasciculatus complex show that its component taxa rep-resent various stages in thallus growth and elaboration, while the subspecific taxa of E. siliculosus are determined primarily by size and shape of plurilocular sporangia. Both species are shown to undergo a streblonemoid phase in their early development. Field observations are confirmed by following the growth of both species in culture. The habitat and host range of both species is found to be wide.

Benthic phases of aCricosphaera sp. (Plymouth Culture Collection no. 156), and of a coccolithophorid obtained from a filamentous plant found growing in the region of high-water mark at Borth, Cardiganshire, have been subjected to a variety of experimental conditions, and viability assessed in terms of their ability to release again the motile cells.

Survival of the benthic cells has been observed in a salinity range of 3–236% with liberation of coccolithophorids directly into the medium at salinities between 3–90 ‰ In the salinity range 90–207% liberation of coccolithophorids was observed on returning the benthic cells to 'normal' sea water after protracted periods of immersion in the media of higher salinities. Benthic cells were found to survive after slow evaporation of the medium and crystallization of the salt around them. Liberation of coccolithophorids has also been obtained after ageing of the culture (e.g. the motile cells have been obtained from an 11-month-old culture). Continued growth of coccolithophorids has been observed at salinities between 6‰. Continued formation of the benthic cells in media of high and low salt concentration resulted in a tendency for the release of coccolithophorids to occur over more restricted salinity ranges.

There are two main types of muscle fibre in the dogfish myotome. Slow fibres make upabout 18 % of the mass of the myotome, the remainder consisting of fastfibres. The slow and fast fibres have a different pattern of innervation, and differ in such respects as their fat and glycogen contents, and in abundance of mitochondria. The two typesof fibre show different responses to depolarizing agents.

Extracellular recordings from the myotomal muscle taken during the swimming of spinal fish show that only slow muscle fibres are active when the fish swims slowly, whereas during vigorous movements, the fast fibres are active. Although both types of fibre contain glycogen, the fast fibres contain only about 50–60 % ofthe amount found in the slow fibres. After a period of vigorous movement, the glycogen levels in the fast fibres fall markedly, whilst those in the slow fibres donot change. The slow fibres contain around 4–5 times the amount of fat found in thefast fibres; after long periods of sustained slow swimming, the fat levels inthe slow fibres fall, and there also may be a slight decrease in the glycogen levels in the slow fibres. Long periods of slow swimming do not alter the glycogen levels found in the fast fibres.

The structure of the tentacle in two species of Pogonophora (of the genera Nereilinum and Oligobrachia) has been investigated by light- and electron-microscopy. The fine structure of the pinnules, epidermal cells and mucous cells is described. The surface membrane of the epidermal cells and the pinnules forms an elaborate system of microvilli which traverse the cuticle and often extend up to the surface particles.

The classical problem of decapod egg-membrane formation and egg attachment was studied in Carcinus maenas, Homarus vulgaris, Nephrops norvegicus and Astacus pallipes. It was found that no fundamental difference existed in the membranes of the above species, and that some of the current views on the physiological processes involved were incorrect. The present study indicated that no externally deposited membranes have been formed around the egg at any stage. The outer-most membrane really consists of three layers which are histochemically distinct from one another and cannot be equated with epicuticle. The outermost layer (layer 1) of this membrane is derived from the vitslline membrane, the second layer (layer 2) is formed through solidification of a fluid exuded from the egg at spawning, and the third layer (layer 3) is formed by highly PAS-positive substance from the egg. It is suggested that the formation of this ‘trichromatic membrane’ is initiated by fertilization.

An earlier paper (Holme, 1961) described the bottom fauna off the south coast of England, as sampled by a modified anchor-dredge. Sampling was later extended to cover the whole English Channel, a further 144 stations being worked, making 311 in all. This paper describes the results of the later survey which, as previously, was concerned mainly with molluscs and echinoderms. Distribution charts for the majority of species identified are given, in which are incorporated the results of both surveys.