Since the appearance of the first documentation of marine algae from within the political boundaries of eastern Canada (South & Cardinal, 1970), a sufficiently large volume of new information has become available to warrant the revision presented here. Taxonomic and systematic changes, together with further additions, corrections and emendations are incorporated as far as possible. A total of 346 species, subspecies and varieties are listed, comprising 131 Rhodophyta, 127 Phaeophyta and 88 Chlorophyta. The treatment is largely restricted to macroscopic forms. Inclusion of microscopic species of Chlorophyta and representatives of other marine Phyla is planned for the future.

The Celtic Sea extends from the south of Ireland and the St Georges Channel across the continental shelf, with the Bristol and English Channels as its eastern limits (Fig. 1) (Cooper, 1967). Although various investigations of the physical oceanography (Matthews, 1914; Cooper, 1967) and zooplankton (Russell, 1934, a, b, 1936; Corbin, 1947; and more recently Southward, 1962; Bary, 1963) of this area have been carried out, there is little or no information on seasonal changes in levels of chlorophyll ‘a’ and inorganic nutrients, and on the importance of tidal mixing in determining these distributions. Since the speeds of the tidal streams range from weak (∼ 0.5 knot) in the northern part of the Celtic Sea to strong (∼ 3 knots) around the Scilly Isles and Ushant (Fig. 2), the vertical stability of the water column as well as the duration of the seasonal thermocline (Pingree, 1975) are likely to be important factors in determining spatial and temporal variations of phytoplankton production. In this paper the influence of water-column stability on phytoplankton distributions (in spring, summer and autumn) in the Celtic Sea is described, using data for temperature, salinity, chlorophyll ‘a’ and inorganic nutrients obtained during seven cruises in 1975. An account of the red tide conditions that occurred in late July to the north-west of Ushant has already been published (Pingree, Pugh, HoUigan & Forster, 1975).

A knowledge of the growth rates and feeding behaviour of planktonic copepods at natural food concentrations is important for an understanding of food-chain dynamics in the sea. In many areas of the open oceans average concentrations of particulate organic carbon rarely exceed 100 µ carbon 1-1, and even in coastal regions the maximum levels are probably only one or two orders of magnitude higher (Parsons, 1975). Thus, most herbivorous marine copepods live in a nutritionally dilute environment (Conover, 1968). In contrast to natural conditions, many laboratory investigations have been carried out at unnaturally high food concentrations, often more than one order of magnitude higher than those which might be expected in the sea.

The majority of barnacles are sublittoral and limited to full strength sea water, but a number of thoracican species are amongst the most conspicuous and successful members of the littoral and brackish-water faunas. Salinity fluctuations are a feature of most littoral and brackish habitats, but the importance of salinity as a stress factor is variable. In many open coast situations, intertidal barnacles are likely to be subjected to lowered salinity levels only when emersion coincides with heavy rainfall or pronounced terrestrial run off. For these animals, behavioural adaptations to prevent irrigation of the mantle cavity by dangerously dilute sea water may be sufficient protection against an irregular, transient factor in their existence, overshadowed in importance by temperature fluctuations and the desiccating influence of aerial exposure.

In an earlier paper (Gibbs, 1973) it was shown that in populations of Golfingia elongata (Keferstein) in the Plymouth area, a significant proportion of individuals possess fewer retractor muscles than is typical for the species. These individuals have three or two retractors instead of the normal four (= subgenus Golfingia) but otherwise are typical G. elongata in all characters. A morphologically similar species G. rimicola Gibbs is also common in the area and this species differs in possessing only two retractor muscles (= subgenus Phascoloides). One possible reason for the presence of aberrant individuals with an intermediate number of retractor muscles is hybridization; if the spawning seasons of the two species overlap in time, then cross-fertilization could be a feasible explanation for this anomaly.

Few investigations into the general biology of associated copepods have been made, although studies dealing with their taxonomy and structure are well documented, for example the many papers of Gotto, Bocquet, Humes and Stock. This work is an attempt to fill certain gaps in our biological information by considering the copepod Paranthessius anemoniae Claus, a cyclopoid associate of the snakelocks anemone Anemonia sulcata (Pennant). First described by Claus (1889) and later by Bocquet & Stock (1959) from Mediterranean waters, Paranthessius has only recently been reported from Irish and British waters (Gotto & Briggs, 1972; Briggs & Gotto, 1973).

Proprioceptive endings associated with the locomotor musculature are apparently extremely uncommon in fishes. Muscle spindles are absent, and only in elasmobranchs have sensory endings of two types been recognized as proprioceptive. One of these, found in sharks, is the coiled corpuscular ending first observed by Wunderer (1908) at the bases of the fins in various species. This type of ending also occurs sub-cutaneously along the body, superficial to the myocommata (Bone, 1964). Lowenstein (1956) examined the responses of the endings associated with the fin bases, and showed that they were slowly adapting mechanoreceptors, functioning as second order proprioceptors since as the fin was bent, so the connective tissue amongst which the endings lie was stretched or compressed, and the receptor discharged.

Since the early 1950s a sport fishery for sharks has existed off south-west England. On average some 5000 sharks are taken annually on rod and line between May and October. The catch consists almost entirely of blue sharks, the majority of which are immature or adolescent females, limited numbers of the porbeagle, Lamna nasus Bonnaterre, mako, Isurus oxyrinchus Rafinesque and very occasionally the thresher, Alopias vulpinus Bonnaterre.

There are few teleosts which depart from the ‘classical’ ichthyan body form to such an extent as the seahorse, Hippocampus. In this genus the caudal fin is absent and the tail has become prehensile, the usual function of the caudal fin is taken over by the dorsal and pectoral fins. The dorsal and pectoral fins both have a sculling action, the small anal fin moves ‘bodily’ through the water from side to side.

In the past, interest has generally centred on fast moving fish, which have evolved a limited number of body forms, as few variations are possible without a sacrifice of speed. The evolution of the swimming mechanisms of these fish has favoured an increase in the maximum speed and acceleration. In relinquishing the demands of speed the seahorse has released itself from restrictions which would limit its possible range of form.

This work is the outcome of an undertaking by the Mechanical Engineering Department to repair and if possible to improve a grab used by the Marine Laboratory. The grab was a type which has a good record of effective sampling on coarse hard sediment as reported by Smith & McIntyre (1954) and fully confirmed by our own experience. Its success in these difficult sediments is believed to be due to the initial penetration provided by the spring-propelled jaws and to adequate weight opposing the upward forces as the lifting cable closes them. Because of wear in the cocking mechanism the machine in question had become dangerous to operate and a number of parts had fractured. Improvements to the cocking/triggering mechanism were successful but it was felt that the repaired striking motion would remain prone to further failure by fatigue and wear. A fair degree of mechanical insight was necessary for effective operation and it was considered fairly laborious to use continuously, so the basic problem was reviewed from an engineering design standpoint with attention to the ergonomic and mechanical problems of achieving a quick turnaround in a small boat such as the laboratory's 10 m coble, and to ensuring durability.

Many types of plankton net have evolved for various sampling needs, but in the main they are designed for sampling in mid-water, or over fine particulate substrates where they can operate within a sledge frame. The conventional plankton nets are mostly towed behind a boat and can only be used in areas where there are no obstacles to impede their course. Many nets are described in the literature and the reviews by Tranter et al. (1966) and the UNESCO monograph on zoological sampling methods (Tranter, 1968) give further details. Nets for taking benthic plankton are generally mounted on a sledge frame and either towed behind a boat (Russell, 1928; Wickstead, 1953), towed in shallow water by persons wading and pulling the net behind them (Colman & Segrove, 1955) or pushed by SCUBA divers (Fager et al. 1966). However, all these methods still leave the need to sample rocky areas and irregular substrates where conventional methods are not possible. Such areas are often extremely rich in planktonic organisms which appear to accumulate within the shelter offered by gulleys and depressions in the bottom topography (personal observation). Often species associated with inshore algal belts are poorly represented in conventional offshore plankton samples (Russell, 1973), and it may be that such species spend much of their larval existence close in shore or in association with shallow water reefs. The present paper describes a diver-controlled plankton net which has been designed to sample rocky areas. By having direct diver control this plankton net can be used to sample other areas where conventional methods are not appropriate.

It has long been known that the corneas and lenses of some vertebrates are yellow in colour, and therefore affect the spectral quality of the light that reaches the retina. Various functions have been attributed to such intraocular yellow filters, such as the reduction of scattered light, chromatic aberration, and ‘glare’; and also possibly an increase in the contrast of some objects viewed against certain backgrounds (see Walls & Judd, 1933; Muntz, 1972, for reviews). It is of course likely that the yellow filters of different animals serve different functions, but it is also clear that in all cases, by absorbing a proportion of the incident illumination, they must reduce the animal's absolute sensitivity. In agreement with this, there is a general tendency for animals with yellow filters to be diurnal, and occupy brightly lit environments. Among the fishes in particular, there is a tendency for yellow lenses and corneas to be especially common among diurnal groups, which avoid the consequences of the inevitable loss of sensitivity by remaining inactive at night (Muntz, 1973).

We frequently require sensitive bioassay techniques with which to study the effects of marine contaminants at environmentally realistic concentrations. Unfortunately, it is difficult to achieve sensitivity and precision in an organism amenable to indefinite periods of laboratory culture. Results from different laboratories are often extremely variable: LC50 values for the same substance, using the same organism, may differ by two or even three orders of magnitude (Wilson, Cowell & Beynon, 1975). Moreover, some of the most sensitive bioassay organisms require nutrient media, which may alter the availability and toxicity of metals by complexing them (Jones, 1964; Kamp-Nielsen, 1971; Hannan & Patouillet, 1972) and often contain metal impurities at significant levels (Albert, 1968; Steeman Nielsen & Wium Anderson, 1970). The object of the work reported here has been to develop a technique by which these problems might be minimized or avoided. Hydroids were chosen as bioassay organisms for a variety of reasons. They are tolerant but sensitive to small variations in their chemical environment. Techniques for growing hydroids are simple and they can be cultured under conditions of near optimal temperature, salinity and food supply, thus minimizing the errors frequent in bioassay work arising from variations in the history of the test organisms, their size, sex or physiological state. An important source of variability in all work with organisms is that inherent in the genetic material, but with hydroids this can be avoided by the use of a single clone.

It is known that vertebrate lysosomes can sequester and concentrate metal ions including copper, mercury (and organic mercurials), lead, zinc, tellurium, iron, nickel, silver and plutonium (Koenig, 1963; Rahman & Lindenbaum, 1964; Scheuer, Thorpe & Marriott, 1967; Vaughan, Bleaney & Williamson, 1967; Verity & Reith, 1967; Barrett & Dingle, 1967; Abraham, Morris & Smith 1967; Slater, 1969; Brun & Brunk, 1970). Allison (1969) states that the accumulation of certain metal ions within lysosomes may labilize the membranes under certain conditions. Furthermore, Goldfischer (1965) suggests that the toxicity of copper may not be fully manifested while it is contained within the lysosomes, but overloading of the storage capacity, or damage to the lysosomal membrane, resulting in liberation of copper into the cytoplasm could lead to cell injury. The haemocytes of Ascidia pygmaea have also been shown to accumulate pentavalent vanadium in a process involving sequestration by lysosomes (Kalk, 1963). It follows that quantitative cytochemical measurements of certain aspects of lysosomal function might permit the detection of responses to toxic materials at concentrations below those to which the whole organism would respond.

During his studies on the Cirripedia Darwin (1854) gave much attention to the Chthamalidae, and his views of the species remained unchallenged for many years. Darwin's attitude to speciation appears to have been coloured by his concurrently developing theories of natural selection, and he was especially interested in the existence of wide variation within species. Thus Chthamalus stellatus as described by Darwin consisted of a number of races or varieties, and was of almost worldwide distribution (‘southern England, Ireland, Isle of Man, Mediterranean, Madeira, Cape Verde Is., southern United States, West Indies, Brazil, Rio Plata, Red Sea, Philippines, China, Gulf of Korea, Oregon or N. California’). This distribution has been considerably narrowed in the last 60 years, and recent investigators have raised varieties to specific rank, or described new species and subspecies. In North California and Oregon we now have the full species C. dalli (Pilsbry, 1916); along the eastern coast of U.S.A. we now have C.fragilis (Pilsbry, 1916); in the Caribbean and along the east coast of South America we have C. angustitergum and C. bisinuatus (Pilsbry, 1916; Ross, 1969; Southward, 1975); for the Indopacific region there are now the species C. challengeri and C. malayensis (Hoek, 1883; Pilsbry, 1916); and in the Mediterranean, C. depressus (Poli), which was reduced by Darwin to a variety of C. stellatus, has been raised again to specific rank (Barnes, 1956; Utinomi, 1959; Southward, 1964; Klepal & Barnes, 1975) and is now assigned to the genus Euraphia (Newman & Ross, 1976). Thus except for a few dubious records what remains of Darwin's C. stellatus is confined to Europe, N. Africa and W. Africa (Southward, 1964; Stubbings, 1967). Nevertheless, even such a reduced distribution encompasses several distinct climatic zones, and seems more extensive than the individual ranges of the three species (C. dalli, C. fissus and C. panamensis) found in comparable climatic regions of the N.E. Pacific.

Luminescence in decapod crustaceans may be of two kinds. Either a secretion is ejected into the surrounding water as a luminous cloud, or specific light organs, which may be internal or superficial, glow steadily (Balss, 1944). There may be more than 150 photophores in some species of decapod, and the number, position and development of these organs in Systellaspis debilis and species of Sergia have been described by Coutière (1906), Kemp (1910a), Terao (1917) and Gordon (1935). The production of luminous clouds has been observed in the Oplophoridae, Pandalidae and Thalassocarididae of the Caridea, and in the Penaeidae of the Penaeidea (Table 1). Observations of the luminescence of specific light organs or tissues are much less numerous. Luminescence has been observed among the Oplophoridae from the photophores of species of Systellaspis and Oplophorus and from the liver of Hymenodora. The hepatic organs of Parapandalus of the Pandalidae have been seen to luminesce, and among the Penaeidea both the hepatic organs of Pesta of Sergestes and the superficial organs of Sergia have been seen to emit light (for references see Table 1). Undoubted hepatic light organs also occur in Chlorotocoides and Thalassocaris of the Thalassocarididae, and superficial organs in Hymenopenaeus debilis of the Penaeidae. Additional organs of doubtful function which have been described as possible photophores occur on the chelae of the homolid crab Hypsophrys, in the branchial chamber of Sergestes, the pleopods of Parapandalus and the uropods of Acetes (Table 2). There are unconfirmed reports of luminescence in the eye of Pasiphaea etarda (Kiernik, 1908) and in Polycheles (Alcock, 1902) and Leptochela (Chace, 1940), neither of the latter two cases being ascribed to a particular organ, though ‘a greasy glandular patch’ near the oviduct was implicated in Polycheles.

Much valuable information on aquarium systems was assembled in the published papers of the 1960 1st International Congress of Aquarology held in Monaco. To date no further congress has been held but Clark & Clark (1964) have collected together a number of papers on sea-water systems and a number of institutes have published details of their aquarium designs, e.g. for the Marine Biological Association at Plymouth (Wilson, 1960), Biologische Anstalt on Helgoland (Anon, 1959), Fishery-Oceanography Center at La Jolla (Lasker & Vlymen, 1969), Marine Laboratory, Aberdeen (Hawkins, 1971) and Sea Research Institute on Texel (de Blok, 1975). A very ambitious aquarium at Dalhousie University, Halifax - the Aquatron Laboratory - has not been fully described although a pamphlet giving some information is available from the curator, Dr Carl Boyd.