The adults of three new cyclopoid copepods are described and figured, namely Micropontius ovoides, gen. et sp.nov., occurring on spatangid echinoids; Lichomolgus leptodermatus, sp.nov., and Conchyliurus cardii, sp.nov., both associated with pelecypod molluscs. Micropontius is made the type of a new family, the Micropontiidae.

Some other copepods, Asterocheres violaceus (Claus), Scottomyzon gibberum (T. & A. Scott), Pseudanthessius liber (Brady & Robertson), Bomolochus confusus Stock, Euryte longicauda Philippi var. minor T. Scott and Peniculus fistula Nordmann, are recorded for the first time from the Plymouth region; and mention is also made of Tisbe elongata (A. Scott).

Points of interest in the biology, morphology, systematics and distribution of all these are discussed.

Recently Jones & Wills (1956) have related the attenuation of light in the sea and in estuarine waters to the concentration of suspended solid matter. The attenuation was measured with an in situ hydrophotometer with a beam acceptance angle of approximately 3.20°. The concentration of suspended materials was determined by filtering in the case of natural samples or by adding known weights of kaolin or mud to tap water. In the discussion of their data and methods they have made application of the difFraction theory for opaque particles relatively large compared to the wave-length of light.

A comparison is made of oxygen and phosphate data from the Fladen Ground. It is found that the conversion factor for oxygen:phosphorus given by Sverdrup et al. (1942) does not agree with the changes below the euphotic zone and an alternative factor is calculated. Problems concerning surface exchange and production are also discussed.

Organic production in the sea can be measured by studying the changes in phosphate throughout the water column. Results obtained by this method are compared with estimates of carbon uptake using 14C made on the Fladen Ground during 1955 and 1956. There is good general agreement between the two methods but some differences in the vertical distribution.

The results are also used to calculate filtering rates of phytoplankton and sinking rates of zooplankton, and to compare observed and predicted vertical distributions of chlorophyll.

Techniques for the rearing of monogenean larvae are described.

The new term ‘oncomiracidium’ is proposed for the larvae of monogenetic trematodes.

Eleven new oncomiracidia offish parasites are described, bringing the total now known to thirty-five.

These oncomiracidia are tentatively classified, and the classification is compared with the existing classification of adult monogeneans.

Elytra of polynoids show two kinds of luminescent responses, viz. a quick flash (duration ca. 100 msec) and prolonged glow (duration 0·25–10 sec). Quick flashes are produced by nervous excitation; prolonged glow responses accompany or follow fast repetitive flashing, or are elicited by strong electrical stimuli. Anaesthetized isolated elytra still give the prolonged glow response when electrically stimulated. Facilitation is also evident in consecutive glow responses. From these various observations it is concluded that the prolonged glow response can be produced by fast repetitive nervous excitation or by direct electrical excitation of the photocytes. The occurrence of facilitation in glow responses of anaesthetized elytra raises the problem whether the same phenomenon in consecutive normal flashes may be due to intracellular changes taking place within the photocytes.

Luminescent polynoids emit light from their elytra. These structures are arranged in two longitudinal rows covering most or all of the dorsal surface of the worm. Light emission is evoked by stimulation and appears as a single flash or series of flashes (Nicol, 1953, 1957).

When a polynoid is subjected to tactile stimulation, scales anterior and posterior to the stimulated region emit flashes. The response is a reflex, the excitatory pathways of which involve peripheral receptors, nerve cord, and a peripheral ganglion in each elytrum on the efferent side of the arc (Bonhomme, 1942; Nicol, 1954).

In 1902 Ernst Vanhöffen drew attention to the occurrence of eight dark pigment spots in Atolla which he thought might be excretory organs.

It is shown that these spots are a specific character occurring only in some specimens, and medusae with this character have been named Atolla vanhöffeni n.sp. This species can now be distinguished from A. wyvillei by other characters.

A study has been made of the feeding activities and reproductive behaviour of the copepod Ascidicola rosea within one of its ascidian hosts, Corella parallelogramma.

Ascidicola rosea feeds on particles which it removes from the food string as the latter is passing through the oesophagus of the host. When active feeding is not taking place, the copepod remains quiescent in the oesophageal bend. An inverted position within the oesophagus is sometimes adopted; this is generally associated with a meagre development of the food string. Certain peculiar structural features—notably the spinous pad on the penultimate segment and the long endopodal setae—are considered to be adaptations which assist the copepod while clinging to the food string.

The eggs of A. rosea are deposited in the ascidian's stomach and the nauplii pass through the host's alimentary canal still enveloped by the inner egg membrane. On reaching the anus, hatching takes place and the nauplii are expelled from the atrial siphon. There are four naupliar and two copepodid stages. Free-swimming life lasts for about 6 days.

In many if not most species of crabs (but not quite all) there is a limit to growth, when no more moulting or ecdysis is possible in normal circumstances. This condition of permanent anecdysis is known as the terminal anecdysis. In the spider crab Maia squinado, the last moult is the moult of puberty, when the animal finally attains sexual maturity, and this moult has different biometrical characteristics from the others. In Carcinus maenas, in contrast, the moult of puberty takes place when the animal is quite small and may be succeeded by about ten further moults before the terminal anecdysis begins.

The immediate cause of the cessation of moulting in Maia squinado is shown to be the degeneration of the Y-organ, which secretes a moult-promoting hormone. In the absence of this gland and its secretion moulting can no longer continue. In Carcinus the Y-organ does not degenerate after the final ecdysis and the cause of the cessation of moulting is to be sought in the excessive production by the X-organ-sinus gland complex of the moultinhibiting hormone. This effectively prevents moulting from proceeding Removal of the X-organ-sinus gland complex in Carcinus allows ecdysis to continue, so that giant crabs can be produced in the laboratory by this means, and at the same time the life-span may be increased. The operation has no such effect on Maia. In either species injection of Y-organ extracts produces transiently the first signs of an approaching moult, in the form of a heightened blood-calcium level. In Carcinus repeated injection led to eventual ecdysis. The presence of the Y-organ is shown to be necessary for removal of the X-organ-sinus gland complex to stimulate moulting in Carcinus.

Two separate methods of producing terminal anecdysis exist in crabs, both involving the hormones which normally regulate the moult cycle, but no reason is known for the existence of the phenomenon.

The rate of filtering has been examined in a series of sabellids and serpulids of widely different size, using suspensions of colloidal graphite and algal cultures. The filtering rates have been expressed as individual rates, as the volume strained per unit fresh weight, and per unit weight of the crown. It may be concluded that the smaller fan worms filter at a relatively higher rate than the larger. This is achieved partly by the relatively larger crown. Free swimming algae escape through the crown; only inert particles down to 1–2 μA are retained, implying that fan worms depend on suspended detritus alone. The filtering rates are briefly compared with those of Chaetopterus and some other filter-feeding invertebrates.

Temperatures and salinity, phosphate, total phosphorus and silicate analyses of water from the International Hydrographic Station E1 during 1955 are discussed. The seasonal variation is shown, and it appears that consumption of nutrients by plants in the spring was: phosphate 0·42 μg atom P/L, ‘total phosphorus’ 0·40 μg atom P/l., silicate 2·43 μg atom Si/1., these being means for the whole water column. Some irregularities are pointed out; they are probably attributable to changes in the water mass.

The range of temperature over which the cirri were active, and the frequency of beating of the cirri at different temperatures were measured in a further five species of barnacles from a variety of habitats. In three of the species the temperature range and frequency of cirral beat were related to the geographical distribution of the species. The tropical and warm temperate species Balanus amphitrite was active at higher temperatures, and showed a greater frequency of beating than the northern species B. balanus; conversely, the latter was active to much lower temperatures than JB. amphitrite. The species with the widest geographical range, B. improvisus, showed cirral activity over the widest range of temperatures, although its behaviour at high temperatures was similar to that of the related species B. amphitrite. It is suggested that B. improvisus is a tropical species that has adapted itself to colder climates; its tolerance of a wide range of temperatures may be associated with its tolerance of low salinities.

The stalked barnacle Lepas anatifera showed too restricted a temperature range for its supposed world-wide distribution, and it is suggested that the species may contain physiological races adapted to different climates. The extremely restricted range of temperatures over which the cirri of the deepsea barnacle Hexelasma hirsutum were active can be correlated with the almost uniform temperature conditions at great depths.

In B. balanus age-groups can be clearly distinguished by growth rings on the shell, and the cirral frequency was found to be slower in the older specimens. Even slower cirral beating was found in some starved specimens.

Samples of twelve broods of oyster larvae were subjected to a standard laboratory rearing technique while other samples were assayed for glycogen. The glycogen reserves of the larvae at liberation lay between 13·4 and 15·4% of the dry organic matter. No correlation was observed between the glycogen reserve and either the size of the larvae at liberation or the yield of spat in the rearing experiments

Details are given of the breeding biology, including the fecundity, of the Long Rough Dab deduced from samples taken in the Clyde Sea area from October 1953 to April 1955. Where possible breeding is related to the condition of the fish; the index of condition is based on the length-weight relation.

The weight of Long Rough Dabs of each sex and stage in maturity increases as a power, slightly greater than the cube, of the length. An annual cycle of fluctuations of this power is seen in the immature females, and indicates how changes in condition at different seasons affect the different size-groups. The measure of condition is taken as the expected weight of a 20 cm Long Rough Dab, and the changes in this weight are followed through the sampling period for males and for immature, maturing and spent females. All groups tend to be in best condition during November and December followed by a decline to the spawning time, in March and April, after which there is a slow recovery.

The variation in the fecundity of a fish species from year to year has not received much attention, although the changes in the numbers of young fish in the plankton are well documented for the Plymouth area (Russell 1930–47; Corbin, 1948–51). The most important work considering fecundity fluctuations is that of Simpson (1951) who, working onPlaice, Pleuronectes platessa L., concluded that during 1947,1948 and 1949 there was a steady decrease in the number of eggs laid, this being due to a decrease in the mean size of the spawning fish which he showed to be correlated with the egg numbers. Simpson's interest in the fecundity was to provide a more accurate estimate for determining the number of plaice in the total population from planktonic egg surveys similar to the work of Buchanan-Wollaston (1923). He did not consider in detail whether the fecundity for a given length might change from year to year. It is this problem which will be considered here. Estimates of fecundity of Long Rough Dabs, Hippoglossoides platessoides (Fabr.), will be analysed, and Simpson's Plaice data will also be considered.

A study has been made of the ecology of the small intertidal lamellibranch Lasaea rubra at various tidal levels at Plymouth and Wembury. In addition, experiments have been carried out to investigate physiological and behavioural differences arising from varying amounts of submersion at different tidal levels, and the following findings have been made.

During the first hour after their submersion by sea water, L. rubra from high up the shore filter at a rate approximately twice that of animals which live lower down. After 2 h, however, both sets of animals filter at the same rate.

High-level animals respond significantly faster to wetting by splash and can tolerate a considerable range of salinity. They also respire at a rate approximately twice that of low-level animals. Respiration, however, is not detectable when the animal is not immersed in sea water.

The taxonomic status and nomenclature of the hermaphrodite forms of Fucus (other than the alga currently known as F. spiralis L. and certain hybrid forms) usually included under the name Fucus inflatus L. by European authors, but under several specific names by N. American and some other authors, is discussed. It is considered that the numerous forms described are best interpreted for the present as forms of a single, extremely plastic and widely distributed species.