Some marine ciliates, chiefly belonging to the genus Cothurnia are recorded from Plymouth and figured. Three new species are described.

Little has been published on the Ciliata from Plymouth waters. The publications of de Morgan (1925, 1926) alone provide a detailed description of some species. In the last edition of the Plymouth Marine Fauna (Marine Biological Assoc, 1957) many species have been recorded not described by de Morgan but which were occasionally mentioned in the works of other authors, and included those investigated by the present writer during her visits to the Plymouth Laboratory in the years 1953 to 1963. Recently, a list of Protozoa observed at Plymouth has been published by Lackey & Lackey (1963).

Direct observations on the reflecting layers in the tapetum of the spur dog Squalus acanthias confirm the orientations of the tapetal reflecting cells which were previously found histologically (Denton & Nicol, 1964). Surface views of the tapetum show the outlines of the exposed surface of the tapetal plates as ‘polygons’. The long axes of these polygons are parallel with the plane of the tissue on which they lie and the polygons are only inclined to this plane across their short axes. The angle to which they are inclined increases as we move towards the periphery of the eye.

A light and electron microscopical study has been carried out on the morphology and microanatomy of two marine species of Heteromastix and less completely on two freshwater samples from the same genus, one only of which is named; this one is, however, important as the type species of the genus (H. angulata Korsh.). Agreement in salient features indicates that Bipedinomonas N. Carter andAnisomonas Butcher, under which the marine species were previously described, should be discarded as later synonyms of Heteromastix Korsh. Apart from the nomenclatural clarification the most important new findings concern the details of the periplast on cell body and flagella, the presence of stellate scales as well as plate-scales on both types of surface, the presence within the body of a starch shell not giving the normal colour reaction with iodine, and of a characteristic fibrous ‘root’ joining the flagellar bases to the plastid surface. A major finding of electron microscopical interest is the clarity with which the formation of scales and of flagellar hairs has been traced to the Golgi cisternae. These observations are an important addition to previous knowledge concerning genera of related green flagellates possibly referable to the class Prasinophyceae.

The morphology and microanatomy of two species of Platymonas have been investigated and certain stages of cell division studied. The anatomical features closely resemble those recently described for the motile phase of Prasinocladus except for characteristic differences in pyrenoid structure (cf. Parke & Manton, 1965). The flagella ofPlatymonas are indistinguishable from those of Prasinocladus, being covered with two layers of scales beneath a layer of structureless mucus which obscures their presence except in sections. Caducous hairs resembling those ofPrasinocladus and related genera are also borne on the flagella.

An electrophoretic study of whole blood samples revealed the presence of haemocyanin and of various other proteins in the blood of fifteen species of marine and terrestrial amphipods and isopods.

The amount of haemocyanin per 1 mm3 of blood is independent of body weight over a range from 10 mg to 1 kg.

Under laboratory conditions and during starvation the haemocyanin level of the blood is lowered as compared with freshly caught specimens.

No relationship between moulting stage and haemocyanin content could be established in three oniscoid isopods, representing Ligia, Oniscus, and Porcellio.

In some species the densities of both haemocyanin and ‘slow proteins’ (i.e. proteins between starting line and haemocyanin) seem to vary in more or less the same direction, over at least part of the total range of variability. In the offshore Conilera, however, an indirect relationship seems to exist between these two protein fractions. This is reminiscent of the situation in Maia squinado described by Zuckerkandl (1960).

The slow protein fractions appear to play a number of roles in the species investigated. In Conilera they consist of various copper proteids (perhaps concerned with the synthesis of haemocyanin?), while in intertidal amphipods and some isopods they carry chromophilic groups that may be of importance in mechanisms of colour change. The colour of the blood of a given specimen of Orchestia gammarella and Marinogammarus marinus depends on the amount of the faster moving, blue chromoproteid present in the blood. These chromoproteids are considered to be carotenoproteids.

The production of extracellular carbohydrate has been studied in Isochrysis galbana and Prymnesium parvum in axenic culture. Increased extracellular production of carbohydrate occurred at reduced and increased salinity, low light intensity and under conditions of nitrogen starvation in Isochrysis, and in some cases appeared to be associated with the sedimentation of the cells from stagnant culture. Extracellular carbohydrate production was found to be greatest during the early and later stages in growth and dropped to a minimum during the mid-growth phase. Experiments indicated that the cells were not being damaged during harvesting of the cultures. A close similarity was found between the monosaccharide components of the intra- and extracellular carbohydrate after acid hydrolysis; both contained glucose, galactose, arabinose, xylose and ribose. It is suggested that the production of most of the extracellular carbohydrate is due to the passive release of organic matter from dead or dying cells.

The type species of Prasinocladus has been re-investigated in cultured material from the Devon coast and studied electron-microscopically by whole mounts and by sections. Salient findings include: the presence of two layers of scales together with characteristic hairs on all four flagella; the arrangement of the flagellar bases in a row, and of characteristic flagellar ‘roots’; the presence of an unusual condition of the pyrenoid with respect to the nucleus; and the structure and behaviour of the theca as different from that of an ordinary cell wall. It is concluded that the genus could appropriately serve as the type of a group to include all known genera and species of monads containing chlorophyll b that possess scaly flagella, but no recommendations are made as to whether the name Prasinophyceae (Christensen, 1962) should be restricted to these or be permitted to cover other known green flagellates lacking scales on their flagella. This investigation is continuing.

The preoccupation of many workers in recent years with the detailed analysis of the settlement behaviour of the larvae of numerous sedentary invertebrates has contributed significantly to our understanding of the various factors influencing the secondary orientation reactions of animals as formulated by Fraenkel & Gunn. Investigations with the planula larvae of hydroids along these lines has hitherto been largely ignored. The intertidal hydroid Clava squamata Müller has a distribution restricted to the larger fucoids in the littoral zone and during the summer months liberates its planulae in large numbers.

Detailed examination of the distribution of colonies indicated that the planulae probably possess clearly defined patterns of behaviour which assists them in locating substrates suitable for colonization. The planulae which are released in response to light are normally found to be photopositive on inert surfaces and to settle photopositively. On Ascophyllum, however, the normal substrate in nature, the older larvae are photonegative. The crawling activity of the planulae is considerably influenced by the texture and contour of surfaces. On rough and pitted surfaces activity is considerably reduced indicating a thigmokinetic response of the larvae. Water currents influence behaviour, planulae orientating positively to the direction of flow. The possible significance of these patterns of behaviour in the substrate selection and distribution of the species is discussed.

Evidence is presented that eggs and sperm of Spirorbis borealis are shed through the nephridioducts, and that fertilization occurs externally to the body but inside the tube.

The eggs fail to develop in vitro unless sperm is present. In individuals collected in winter and maintained at 15 or 19° C, the male and female gonads mature more or less simultaneously. Among groups of individuals sperm is usually shed first and soon afterwards a large proportion may be observed to have extruded ova.

A pair of rays caught by line from 1300fm westward of the English Channel have been identified as Raja richardsoni Garrick known only from the type specimen also taken by line in New Zealand waters from about the same depth. The Plymouth rays agree well with the New Zealand fish in proportional measurements, in bearing denticles on both surfaces, and in the absence of spines but differ slightly in colour, in their smaller number of teeth, and in the greater development of a lateral process on the nasal flap.

Two phases, cyst and motile, of three species of Halosphaera (Prasinophyceae), H. viridis Schrn., H. minor Ostenf. and H. russellii Parke, sp.nov., are described and the distinguishing characters tabulated. The stages in development of the two phases are detailed and a possible periodicity in their production is suggested. Only the motile phase can persist as an independent form reproducing asexually by fission. Sexuality is not recorded for the genus nor can the reported production of aplanospores be substantiated. The supposed ‘heterokont motile phase of Halosphaera’ of Pascher, who placed the genus in the Xanthophyceae, is believed to be a colourless phagotrophic flagellate parasitizing the cyst phase. All cyst phases, with plain or punctate walls, resembling those of Halosphaera in structure, do not necessarily belong to this genus. The study of living material is therefore essential.

A series of nineteen different biometrical characters have been measured on the scutal and tergal valves of the boreo-arctic Balanus balanoides collected from over its whole area of distribution; these values attempt to define the shape of the valves.