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A summary is given of the distribution of Balanus balanoides (L.) and of earlier work on differences — racial and otherwise. The variation in the date at which different populations are fertilized is considered. Data are given on the time required for the development of the embryos of this species in vitro at 10 °C, with eggs from a number of populations from the eastern and western Atlantic and examined soon after collection, and also after transplantation and maintenance under ambient laboratory conditions over the next breeding season. Both aspects of reproduction are under genetic control. There is no correlation between the date of fertilization and the time required for development. Oocyte and egg size appear to be largely controlled by temperature. On both sides of the Atlantic there is a general tendency for the time of development to decrease with decreasing latitude. The population at Millport, Scotland appears unusual. The southernmost populations on European shores resemble those at the extreme south in North America. A study of the effect of temperature has shown that at lower temperatures the time of development of the embryos in vitro from all populations tends to be the same; the difference lies in the Q 10 values. The results are discussed relative to palaeontological data and the existence of clines in other features.

The effect of hypo- and hypersaline media on the development of the embryos of the common cirripedes, Balanus balanoides , (L.), B. crenatus Brug., B. balanus (L.), B. perforatus Brug., Chthamalus stellatus (Poli), and Elminius modestus Darwin has been examined. These species represent littoral and sublittoral, boreo-arctic and warm-temperate, relatively steno- and euryhaline, and steno- and eurythermal forms. The range of salinity over which the embryos would develop to give free-swimming stage I nauplius larvae, no matter at what stage of development the cultures were started, was similar in all species, namely 15–20 to 40%. Low-salinity media cause cytolysis while high salinity media give grossly abnormal embryos which may, however, develop further. There seems little direct relation between salinity tolerance and that of the habitat in which the animals are found; a capacity for acclimation may be more important. The causes underlying the production of abnormalities are discussed.

The details of morphology of the six naupliar stages of Balanus hesperius are described, the material being referable to the forma laevidomus of Pilsbry. The nauplii are particularly characterized by a long and somewhat slender body and rather stiff appendages, the rami of which are thickened proximally. The general pattern of development conforms to that of other nauplii and is remarkably similar in all balanids. Tables of sizes and setation are given.

New records for Elminus modestus Darwin, and a single one for Balanus eburneus Gould are given for the western coast of France. The local population of B. balanoides (L.) at Arcachon (Gironde) has increased in extent and population density over the past few years; a curious growth form of this species — probably resulting from intense competition with Chthamalus stellatus (Poli) — is described.

[La relation entre la teneur en eau et la respiration des tissus du corps, avec reference au cycle de mue, a ete determinee pour Balanus balanoides. La teneur en eau et le quotient respiratoire presentent un cycle en correlation avec le cycle de mue, qui est analogue a celui decrit pour beaucoup d'autres Crustaces. Une comparaison avec d'autres Crustaces montre un maximum plus eleve dans la teneur en eau, ce qui est en relation avec l'absence d'un exosquelette calcifie, la rapidite de la mue et la faiblesse relative de l'accroissement de taille a la mue. Le cycle de respiration ressemble etroitement a celui de Palaemon serratus (de Naples), et d'autres analogies laissent supposer que les mecanismes de controle puissent etre les memes dans les deux cas. Le controle hormonal de ces processus est discute., La relation entre la teneur en eau et la respiration des tissus du corps, avec reference au cycle de mue, a ete determinee pour Balanus balanoides. La teneur en eau et le quotient respiratoire presentent un cycle en correlation avec le cycle de mue, qui est analogue a celui decrit pour beaucoup d'autres Crustaces. Une comparaison avec d'autres Crustaces montre un maximum plus eleve dans la teneur en eau, ce qui est en relation avec l'absence d'un exosquelette calcifie, la rapidite de la mue et la faiblesse relative de l'accroissement de taille a la mue. Le cycle de respiration ressemble etroitement a celui de Palaemon serratus (de Naples), et d'autres analogies laissent supposer que les mecanismes de controle puissent etre les memes dans les deux cas. Le controle hormonal de ces processus est discute.]

An account is given of the further spread of Elminius modestus along the German coast north of the Elbe towards the Danish coast. The population at Cuxhaven has spread to the outer estuary and Balanus balanoides is at several places in danger of extinction. Elminius modestus is now well established in several small harbours as well as on parts of the open coast between Cuxhaven and Dagbuller Hafen. The harbour populations have most probably been established by shipping but some marginal dispersion is taking place at suitable places. The species is absent north of Dagbuller Hafen: it has not yet reached Danish waters either by marginal dispersion or by a vector carrying it into any of the ports. Elminius modestus has not reached the north-eastern German coast.

The seasonal changes in the body weight and composition of two common boreo-arctic species of cirripedes, Balanus balanoides and B. balanus have been followed.At a constant size (age under constant growth conditions) the body weight is closely related to the season. Increase in body weight takes place rapidly during the spring as reserves are laid down. These reserves are subsequently utilized for gonadal development.The changes in B. balanus are more gradual than in B. balanoides and probably reflect differences in the habitat conditions.The reserves, although contributing to the gonads, are not themselves adequate for their total tissue.

There is some reduction in oxygen uptake of isolated bodies on starvation when carbohydrate is being utilized.There is a gross discrepancy between the oxygen demand as measured in isolated bodies and the available substrate; respiration is probably reduced during inanition.It is suggested that the moulting cycle is coupled to the metabolic activity in an obligatory fashion rather than being dominated by the kind of hormonal control found in decapods.

The QO2 of three common cirripedes has been measured at four temperatures and on each of four occasions during a year: dissected bodies were used. Statistical analysis indicates that only infrequently is the Q10 weight dependent. Such dependence seems to be related to the nutritional conditions in the environment rather than to the internal state or species habitat. Q10 varies widely even in a given species. In Balanus balanoides there is a marked homeostasis at certain seasons as there is in Chthamalus stellatus at other seasons: Balanus balanus shows somewhat less marked homeostasis. A low Q10 of basal metabolic rate in littoral invertebrates has been observed by others in a variety of animals. The results of some relevant previous work are critically examined and compared with those of the present investigation.

The effect of starvation for various periods and also at various times during the development of the ovaries of Balanus balanoides (L.), followed by feeding, has been investigated. The total feeding time to full maturation shows little variation. The time at which the egg masses are laid down can, however, be to some extent manipulated by controlling the starvation period.

It is difficult to determine the weight or nitrogen content of the living tissues of an operculate barnacle without destroying it. It has been customary, there-fore, in ecological work to express growth in terms of various parameters determined from repeated measurements of the shell. Moore (1934) employed shell volume calculated from the height and basal diameters; others (Costlow & Bookhout, 1953, 1956; Mawatari, Hirosaki & Kobayashi, 1954a, b) have used the area of the basis. Most commonly, however, in growth-rate studies the length of the basis measured through the rostro-carinal axis has been used (Hatton, 1938; Barnes & Powell, 1953). Recently, working with animals cultured in the laboratory when the cast of an individual could be obtained subsequent to ecdysis, Costlow & Bookhout (1957) have used the size of the mouthparts as a measure of growth after first establishing their relation to body size. The space, both areal and volumetric, occupied by a sedentary animal is of primary importance in studies of its ecology and measurements of shell-size are, therefore, adequate for many purposes. For some aspects of growth and ecology it is, nevertheless, very desirable that the relation between such parameters and others, more directly connected with the living material, should be established.

The structure and innervation of the sensory setae which are present in large numbers on the penis of Balanus balanoides (L.) have been established by scanning and transmission electron microscopy. Each seta contains a small number of sensory dendrites surrounded by an extracellular supporting tube which is presumed to be secreted by the enclosing sheath cell. The dendrites, which distally extend beyond both the sheath cell and supporting tube, terminate at the tip of the seta within a pore-like invagination of the cuticle and thus are in direct contact with the environment. Proximally bundles of dendrites pass into the penis tissue where they are surrounded by several sheath cells. The supporting tube terminates at a point within the body of the penis where a series of intracellular rods arise. The ciliary character of the dendrites is evident in this region, the microtubules being organized into the (9 × 2) +2 pattern. It is deduced that the sensilla are chemosensory; their structure is compared with that of other crustacean sensilla which are presumed to be chemosensory.

1. It is shown that the extraction by 5% trichloracetic acid of glycogen from the tissues of some typical marine invertebrates(Balanus balanoides, Nephtys hombergi, Carcinus maenas, Mytilus edulis) is a function of the homogenization procedure. 2. In agreement with work on rat tissues, glycogen fractions cannot be differentiated by their solubility in cold 5% trichloracetic acid. Total glycogen only need be determined.

ChezBalanus amphitrite, espece des eaux chaudes, l'utilisation de l'oxygene par des individus isoles (extraits de leur coquille), soumis a une temperature peu elevee est de forme oscillatoire, contrairement a ce que l'on observe chez des especes des eaux froides. Il se peut que cette difference caracterise de maniere generale deux types d'especes.

The annual growth in temperate waters of a number of cirripedes appears to be very similar: during the first year, rapid growth of the young spat follows the spring settlement and is succeeded by more moderate growth rates as the size increases during the summer; subsequently, in the autumn and winter little further growth takes place. This pattern is repeated annually as long as growth continues. Such a sequence appears to hold for Balanus balanoides (L.), B. balanus (L.) da Costa, B. crenatus Brug. and Verruca stroemia (0. Muller) (see BARNES, 1952-53, 1955 and 1958 a; BARNES and BARNES 1954; BARNES and POWELL 1953) at Millport, Scotland, and similar results have been obtained elsewhere (RUNNSTRbM 1925; HATTON and FISCHER-PIETTE 1932; MOORE 1934; HATTON 1938; BOUSFIELD 1954; CRISP 1954). When the effect of crowding, covering by mud or algae, and extent of intertidal exposure, are eliminated by semi-controlled raft exposures, the growth rate at any time of the year is seen to be particularly under the influence of the amount of food available. Food is particularly abundant during the planktonic phase and during the period when the young spat is growing vigorously. Indeed, it has been shown that in Balanus balanoides synchrony of nauplii release and the spring diatom outburst is achieved over the wide range of its distribution and the mechanism has been

as Maine on the east American coast and to the shores of Britain. While there is a good deal known about its distribution (see BROCH, 1924) with the exception of a recent study of its breeding habits in the Irish Sea -(CRIsP, 1954 there is little detailed information on its general biology. It is a common sub-littoral barnacle in the Clyde Sea Area, being found widely dispersed on suitable rough ground. It has been found at all depths down to 60 metres, and although more commonly between 20-30 metres, this may merely reflect the fact that it is at these depths that suitable substrata occur in this area. Observations have been made of its occurrence in the area, but the regular collections, on which this account is largely based, were taken between Little and Great Cumbrae at a depth of about 20 metres. The distribution does not appear to be regular even over quite a restricted area, but the population density at this point is very high (see later). Samples were taken with a small dredge, the stones and shells being usually covered with barnacles, often distorted from the typical shape because of overcrowding. The tidal currents at this point are quite strong, and this and the rough stony and shelly bottom appear to be excellent conditions for this species. On these grounds B. balanus is often, indeed usually, mixed with the other common sub-littoral cirripede in this area, B. crenatus. The other associated species are those commonly found on this type of mixed rough ground and the following list indicates those most commonly taken.