1. J. H. J. Poole’s neon lamp method (1928) of integrating the photo-electric current is serviceable for work at sea down to moderate depths, which further experience may extend considerably. It is specially valuable for determining the light just above the water, and at such depths down to 5 m., at which the variability of the light renders the potentiometer method (1925) very difficult or quite impossible in rough water. For greater depths, down to 70 m. (bottom in the English Channel around our normal range) we have so far been able to use the latter only.

2. The loss due to the shadow of the ship, obtained by subtracting the illumination just above water from that on the deck-house roof, was found to vary from an extreme case of 52 per cent, and a normal loss of 30 per cent, with an overcast sky, down to 11 per cent with a clear sun at 31° altitude.

3. The loss of light due to its entering the water was found to vary from 7·5 to 16·5 per cent, mean 13·1 per cent.

4. It is desirable that the illumination just above and just below the water surface should be determined by the neon lamp method as a routine.

The effect of light upon plant growth is a problem which has attracted many workers since the discovery of Priestly, in 1771, that a plant could purify fixed air, carbon dioxide, which was followed by the supplementary work of Ingen-Housz and Senebier, who showed that the phenomenon was associated with the nourishment of the plant, and took place only in sunlight and through the agency of the green portions of the plant.

1. Ligia is a nocturnal animal inhabiting crevices in rocks above high-tide level. It is omnivorous though Fucus spp. form the main article of diet.

2. Immersion experiments were carried out in which the animals were subjected to a gradual transition from salt to fresh water. None survived this treatment for more than one month. It was noticed that the reduction in salinity was accompanied by an increase in the rate of beat of the pleopods.

3. Animals were subjected to sudden and gradual changes in temperature. One specimen survived a change from water at 15° C. to water at 30° C. for 28 minutes, but was dead after 78 minutes; a second, changed from water at 15° C. to water at 35° C, was to all appearances dead after 8 minutes, but recovered after being replaced in water at the original temperature.

1. Ligia is an omnivore, though normally feeding on Fucus. Portions of food are cut off by the mandibles and passed into the œsophagus. Its feeding period is limited.

2. The foregut is provided with a number of ampullæ and lamellæ which are furnished with spines and bristles and are so arranged as to form a filter for the separation of the liquid portion of the food from the solid particles.

3. A second filter is found in the floor of the foregut protecting the entrance to the hepato-pancreas.

4. A ventral valve is present preventing the entry into the hepato-pancreas of solid food from the intestine.

5. The hepato-pancreas consists of three pairs of tubules provided with a muscular network for producing contractions. The epithelium possesses discrete cells.

A study of the respiration and of the function of hæmoglobin in Planorbis corneus and Arenicola marina has been undertaken.

The oxygen consumption of Planorbis is of the order of 0·026 c.c. per gm. per hour, measured at 15° C.

The blood volume is approximately 0·581 c.c. per gm.

The combined oxygen of the blood is 0·013 c.c. per c.c. of blood, the total oxygen being 0·014 c.c. per c.c. The total oxygen capacity of the blood per gm. of snail is estimated to be 0·0081 c.c.

The oxygen supplied by the blood is calculated to last 18 minutes and is found by experiment to last 25 minutes.

The snail does not immediately oxidise its hæmoglobin after subjection to anaerobiosis. Oxidation begins after 10 minutes and is complete within 20 minutes.

1. The yellow colours of the hydroids include at least two groups, the carotinoids found in the Antennulariidæ and Haliciidæ and the flavone-like pigments that occur in the Sertulariidæ. From the literature a third group, the uradines, may be added.

2. The flavone pigments and their relatives are all water soluble and are thus distinguished from the carotinoids which are not water soluble, but may be dissolved in the usual fat solvents.

3. In the Sertulariidæ studied, a graded series of chromatophore groups and pigments was found which ranged from the colourless species Sertularia argentea Ellis and Solander, through the yellow of Sertularella gayi Lamaroux and S. polyzonias Linnæus, to the orange-brown of Thuiaria articulata Pallas. The brown of Sertularia pumila is probably also a flavone derivative.

4. The flavones and related pigments occur extensively in the plant kingdom. It is probable that the flavone-like pigments found in the Sertulariidæ are of plant origin.

1. The bacterial content of mud deposits in the Clyde Sea Area has been investigated.

2. The number of bacteria is found to decrease from the surface downwards.

3. The numbers fluctuate very much in the top mud layers, and there is some evidence of bacterial zonation.

4. In the deeper mud layers the bacterial content for any given station is fairly constant.

5. The predominant organisms were found to be water bacteria of the Achromobacter and Chromobacterium type, and large spore-forming bacilli similar to common soil bacteria.

6. The factors affecting the bacterial content of the muds are discussed.

1. Details are given of the results of a series of hauls with the 2-metre stramin ring-trawl fished at six different depths in daylight, at dusk, in the dark, at dawn and again in daylight on June 3rd–4th, 1926.

2. A comparison is given of the results obtained on the four nights July 15–16th, 1924; June 17–18–19th, 1925, and June 3rd–4th, 1926.

3. The importance is stressed of the effects on the type of behaviour shown by any animal produced by the depth at which it is living in the daylight and the speed at which it can swim upwards.

The pteropod Clione limacina (Phipps), now regarded as one of the tectibranchs, occurs at times in the neighbourhood of Plymouth. In 1930, however, it was extraordinarily abundant, especially in the summer, and was breeding freely. Although not specially recorded it has been seen singly or in small numbers in almost any month of the year, and for some years the eggs and larvæ (not recognised at the time as belonging to Clione) have been seen in summer. So far it is known from the British coasts in the North Sea and the west and extreme south-west of England. Its distribution, as known up to 1908, is given fully for the area of International Fisheries Investigations by Paulsen (1910). There it is shown that it is an Arctic-boreal species, spreading southwards nearly to the Bay of Biscay, which is about its southerly limit. It is known to occur in the northern and mid North Sea, but not in the southern North Sea, and at that time was only recorded from the Channel in the extreme west. It is also common in the Atlantic. Paulsen was led to infer that Clione limacina did not enter the North Sea from the Channel, but its prevalence sometimes at Plymouth shows that it can come a long way up the Channel and, as few samples are taken to the east and in the southern North Sea, this view should be carefully reconsidered.

The two species of Nassarius (usually known as Nassa), N. reticulatus and N. incrassatus, are both common at Plymouth. N. reticulatus, the larger species, occurs from low water usually to a depth of a few fathoms, more rarely from the waters outside the Breakwater, N. incrassatus occurring between tide-marks and extending into deeper water, even to 46 fathoms.

In 1926 Pelseneer discovered the eggs of Trivia europea on the French coast. These he found were laid in capsules embedded in the compound ascidian Polyclinum luteum, the molluse biting a hole and laying its eggs in a vase-like capsule completely enveloped in the ascidian except for the wide lip of the vase which projects freely and can be easily seen with the naked eye (Pelseneer, 1926, Figs. 11–12). He also hatched some larvae from these eggs which were very interesting, as they possessed an accessory shell somewhat similar in shape to the Echinospira of Lamellaria perspicua. He did not obtain the eggs directly from the Trivia and was not able to keep the larvæ alive more than a few days. In his paper he expresses the hope that some worker will confirm his observations experimentally. This I am now able to do, having procured the eggs actually laid by the Trivia, hatched them out and kept them alive for more than a week, afterwards collecting the larvæ from the plankton from stages which exactly corresponded with those from the egg up to late stages which metamorphosed into young Trivia, and young stages of Trivia feeding on compound ascidians which corresponded with the metamorphosed forms.

Trivia europea is common at Plymouth between tide-marks and in a few fathoms of water; occasionally further out in deeper water. Records are available from the shore to the region beyond the Eddystone.

Plasmodia of Labyrinthula almost invariably appear in the diatom cultures and other small marine aquaria which I have kept during the last several years for a variety of purposes in Glasgow. These aquaria are stocked with material from Millport, I. of Cumbrae, and I think it quite certain that the Labyrinthula is imported thence.

This amazing creature has attracted interest ever since it was first described by Cienkowski in 1867, and good figures of it have been published by Cienkowski (1867), Duboscq (1921), and Valkanov (1929). The following note is to be regarded as a commentary on previous work and a record of my own observations rather than as an exhaustive account of the organism.

In a small collection of sponges obtained during the winter of 1930–31 at Plymouth, six specimens were found which are of special interest. Four of these have proved to be new to the locality, the fifth was new to British waters, and the sixth was found to be a new species. Those species new t o the Plymouth area are Gellius angulatus (Bowerbank), Pachymatisma johnstoni Bowerbank, Eurypon clavatum (Bowerbank), and Halichondria firmus Bowerbank. The latter is the first example of the species to be recorded since it was first described forty years ago. The species new to the British waters is Reniera aquœductus Schmidt, and the new species Pseudaxinella alleni n.sp.

The insects, Scatella stagnalis, for the present study were collected from the Marine Biological Laboratory at Plymouth at the kind suggestion of Dr. Allen, F.R.S., the Director of the Laboratory, during my short stay there in the summer of 1929. So far as I can see, no work on the early stages of the genus Scatella is available. This led me to put on record the present account of the different pre-imaginal stages of the insect Scatella stagnalis in the following pages. I have described here only those stages that are exhibited in my hurried collection which may not be complete. A study of its complete biology would be of considerable interest; this, however, requires a constant watch of the species at the spot for a fairly long period.

The luminiferous organ of the Macrurid fish Cœlorhynchus cœlorhynchus Risso is described in this paper. It consists of a gland, flattened dorsoventrally, placed in the body-wall, just in front of the pelvic fins. The secretory epithelium is thrown into a series of tubules, projecting downwards from the roof of the gland into a system of collecting spaces: the latter are confluent, posteriorly, with a duct which leads backwards, between the pelvic fins, to the anus. Blind pouches, which run upwards for a short distance beside the rectum, arise from the duct at its external opening at the anus.

In a previous paper (Journ. Mar. Biol. Assoc., Vol. XVII, No. 1, Sept., 1930) I described in detail a series of experiments on Growth and Maintenance in the Plaice which were carried out during 1928 and 1929 at Cawsand, near Plymouth, and at Lympstone, near Exmouth. The purpose of the present paper is to present and discuss data collected at the above places during 1930 in continuing the experiments. The conditions under which the last experiments were carried out were identical with those of 1929, i.e. refined with reference to those of 1928. Several additions were made, however, to the series of 1929. Two fish of each sex were supplied with maximum rations while living under the conditions maintained during 1928 and were segregated in a box, which had the original ½″ mesh wire-netting windows but which was divided up into compartments. This experiment was arranged in order that we might ascertain the possibility of food leakage due to tidal action during the course of the earliest experiments, but it also enables us to compare the results obtained under slightly different conditions of water circulation, which is important in view of the fact that the windows of the modified boxes were of necessity minimal in area.

The aim of the paper has been to treat the data of the Plaice experiments on Growth and Maintenance, carried out at Cawsand and Lympstone during 1929 and 1930, in a statistical manner. The experiments for each sex, year and place have been resolved into experiments with an average plaice during the “average” 14 days of the third growth season. Growth and food-percentage indices have been provided and a fairly high degree of correlation between food and growth has been indicated, and shown to be uniform for the sexes. Regression coefficients indicating the facility with which food is utilised for purposes of growth have been worked out and have been shown to vary with place and year, but not with sex. Maintenance demands have been evaluated and shown to be slightly greater in males than in females. The diminished demands during winter months have also been evaluated. The outstanding features of the results are the distinct differences shown between the Cawsand and Lympstone plaice, which differences it is suggested arise out of size differences to a large extent.

Growth in length during the transition from larva to adolescent in the pilchard and sprat has been analysed, and simple straight-line equations deduced from observed data have been used to demonstrate how the different intervals along the dorsal and ventral surfaces of the body alter in length and proportion as development proceeds.

In the herring, pilchard, and sprat at least one of the body-intervals remains for all practical purposes unaltered in length during the transition. In the herring there are two such intervals, namely, (1) the distance from the back of the brain along the dorsal surface to the insertion of the first dorsal fin-ray, and (2) the distance from the insertion of the pelvic fins along the ventral surface to the anus. In the pilchard and sprat one of the above two remains stationary, but the other increases in length; in the pilchard the fixed interval is the distance from the back of the brain to the first dorsal fin-ray, and in the sprat it is the distance from the pelvics to the anus.

In the herring and pilchard the greater part of each unit of increase in the length of the body ventrally from the back of the head to the end of the caudal peduncle is added in front of the pelvic fins, whereas in the sprat this is added post-anally.

In other papers (Ford, 2 and 3) attention was directed to a study of the changes in length which occur during the transformation of the transparent eel-shaped larval clupeoid into the silvery and scaled adolescent fish. The change in position of the anus and fins relative to the vertebræ was considered in connection with the altering proportions of the different body intervals as development proceeds, and simple models were used to illustrate important features.

Now the freshwater eel has its transparent larval stage and metamorphosis. As in the clupeoid, length-proportions change during development, while anus and fins undergo marked migrations with respect to the myomeres. It was therefore thought to be of no little interest to analyse the length-changes during development in a manner similar to that adopted for the herring, sprat and pilchard. Professor Johannes Schmidt most kindly supplied me with material upon which to work, and I have made much use of data already published by him in reports on his great pioneer investigations. I have also drawn extensively from the data given by Dr. Leon Bertin in his paper on the migrations of the anus in the eels during ontogeny. I may be permitted to add that much which follows is suggestive in nature, rather than proven fact. Nevertheless, it should prove of interest in its direct bearing upon questions of fundamental biological importance.

1. In regard to relative abdomen-breadth and relative carapace-breadth, the common shore-crab Carcinus maenas in both sexes exhibits a continuous change of proportions throughout life, from small animals of 2 mm. carapace-length to the largest obtainable (over 50 mm. carapace-length).

2. The parts measured exhibit constant differential growth-ratios (growth-coefficients) relative to carapace-length taken as standard, over long periods of the life-history.

3. The approximate growth-coefficients are as follows, relative to carapace-length:

Carapace-breadth, 1·06. This appears to be constant throughout the range of size measured, with a possible decline to nearly unity at large sizes.

Abdomen-breadth.

Crabs unsexable externally (2–6 mm. carapace-length), 1·26.

Females: early phase, 1·26; late phase, 1·42.

Males: early phase, 1·07; late phase, 0·94.

The early phase begins as soon as the sexes can be distinguished. The onset of the late phase may be presumed to be correlated with sexual maturity. In females it occurs certainly between 17 and 20 mm. carapace-length, in males between 14 and 29 mm.

4. There are indications of seasonal and local differences in relative abdomen size.

5. Feeding crabs of 9 to 22 mm. carapace-length solely on fresh ox-thyroid or fresh ox-pituitary for periods up to a year produces no change in growth-rate or in secondary sexual characters as against controls fed on fresh fish.