An analysis of the quantity and distribution of unspawned eggs in the gonad of o. edulis recorded in Table IV, 1, 1927 (of oysters with young) and Table IX, 1,1927 (of post-spawned oysters), gives useful information regarding the occurrence and fate of unspawned ova as may be seen from the figures given in Table A.

In August, 1932, marked stratification of the water in the English Channel led to an unusual distribution of minor chemical constituents. Two thermoclines were present, between which high silicate values were found, indicating rapid re-solution of silica as found in former summers; pH was also very high at 15 metres.

In or about December in four years, nitrite in inshore waters has been found much in excess of that present in the open Channel.

The “mean cube Beaufort number” is suggested as a useful practical measure of sea disturbance. Three out of four midwinter plankton outbursts, inferred from a fall in the phosphate content of the water, have followed periods of sunny weather with little wind.

1. The copper content of sea and river waters can be rapidly determined using the sodium diethyl-dithiocarbamate method followed by extraction with chloroform.

2. This solvent takes up only traces of the natural colouring matters found in waters, but blank estimations should be made with some river waters and occasionally with sea-waters on account of the presence of plankton.

3. Carbon tetrachloride can be used instead of chloroform as solvent, it extracts less per unit volume, but the volume recovered is larger, the resultant yield being identical. Amyl alcohol extracts more than chloroform, but the volume recovered is smaller, the resultant yield being about 0-8 times that of the others. The alcohol takes up more colouring matter from river water, does not separate as readily as the others, and floats, whereas they, more conveniently, sink. For work in hot climates its higher boiling-point may be an advantage.

4. In fresh water iron salts in large excess might cause error; this can be checked by the electro-deposition method.

1. Photo-electric cells of the rectifier type are useful for approximate measurements of light intensity, in air or under water, using a lowresistance galvanometer, the current through which may be reduced by a special shunt keeping the circuit resistance constant.

2. Such an arrangement has proved serviceable for shore work, a light gun-metal photometer, housing a cuprous oxide cell, having been carried about by a diver.

3. These rectifier cells can also be used at sea, but instead of the current, the E.M.F. is determined by means of the potentiometer outfit as used at sea in previous years.

In past years during the study of the vertical distribution of macroplankton much information has been obtained on the abundance of the different animals in the catches at different times of the year. Results have already been published to show the seasonal distribution of pelagic young fish (4), and also on the abundance and composition of the Sagitta population (5, p. 565). In this latter study the change over from the predominance of Sagitta clcgans to that of S. sctosa during the years 1930 to 1932 is striking. During the examination of catches it has been noticed that each year has been characterised at some time by the abundance of a species which may occur only in small numbers, if at all, in other years. This has been especially noticeable in the composition of the medusa population. It is necessary to follow these changes through a number of years to see if the presence of certain plankton organisms cannot be used as an index of conditions that may lead to other fluctuations such as those of the fisheries.

1. Fortnightly samples were taken with a fine-meshed net in single vertical hauls at different positions in the Clyde Sea-Area.

2. Each stage of Calanus present, from ovum to adult, was counted, and charts were constructed expressing these results for one year as total numbers and as percentage composition.

3. Calanus passes the autumn and early winter mainly in its Stage V copepodite form.

4. In general, total numbers were high in September, 1931, and fell steadily to a minimum in March; in Loch Fyne the minimum occurred i n April.

5. A sudden increase was observed in May and numbers rose to maximal values; the decline also was sudden.

6. Reproduction began in February and three plainly marked breeding periods were observed between February and July.

7. The time taken by the egg in developing into the adult was four weeks.

8. The total life of a Calanus during the summer was estimated to be about two and a half months; in winter it is five to six months.

9. In Loch Fyne a noticeable lag occurred during the winter and early spring.

10. The number of Calanus present in the autumn of 1932 was considerably less than.at the same time in 1931. This may have been due to a shortage of food.

The size of the cephalothorax in Stage IV, Stage V, and Stage VI Calanus has been measured during the year 1931–1932 at three stations in the Clyde Sea-Area.

In general the size was greatest when the water temperature was low, and least when it was high, but besides this there was a series of increases and decreases in size which were apparently connected with the breeding periods. The Calanus produced at the beginning of a breeding period were large (at Station I) and those produced at the end were small (at Stations I and II). The greatest production of eggs usually occurred when the female Calanus were of small size.

During the autumn of 1931 the Stage V Calanus from Station IV (upper Loch Fyne) were considerably larger than those from the rest of the area, but this distinction had been lost by the autumn of 1931.

Stages IV and V Calanus taken in the top 30 m. were almost invariably smaller than those from deeper water.

The Calanus show a very wide range of sizes, the range for Stage V overlapping those for both male and female. Possible causes of this are discussed.

1. Previous work on vertical distribution and diurnal migration is described.

2. The diurnal migration of Calanus was studied on two occasions in Loch Fyne (January and July, 1932).

3. Vertical hauls were taken every three hours with a closing net dividing the total depth into six sections.

4. The results for each copepodite stage of Calanus are discussed, and January and July conditions are compared where possible.

5. Ova and nauplii were observed to be most abundant in the top 30 metres.

6. Copepodite Stages I, II, and III were most abundant above 30 metres and only the third copepodites showed any tendency to descend as the light increased.

7. Stage IV showed a migration towards the surface at night, but were generally distributed during the next day.

8. It is suggested that the results for this stage are probably confused owing to its transitional nature between the young stages living at the surface and Stage V Calanus living in deep water.

9. Stage V was found always in deep water, slight diurnal changes being ascribed to the presence of such Calanus as were about to moult into adults.

10. Females showed definite diurnal migration in both January and July.

11. Males showed a general distribution and migrated in small numbers towards the surface at night and away from it during daylight.

12. Stage V copepodites and females both lived nearer the surface in January than in July, correlated with seasonal changes in the intensity of the sunlight.

13. The presence of swarms of Calanus at the surface under conditions of bright sunlight is discussed.

Certain diatoms seem to live predominantly on the foreshore. While the pelagic diatoms have received very much study, relatively little attention has been given to the shore forms. There is no satisfactory account of these organisms as they occur on the coasts of Lancashire and Isle of Man, and one may expect that they have much importance as the food of many animals. In a further paper I will deal with this question. For this reason I deal here only with those littoral diatoms found along the Mersey Beach, in the vicinity of Liverpool, and with those collected from the sandy and rocky shore of Port Erin (Isle of Man). Masses of these organisms can easily be recognised with the naked eye, discolouration of the sand and mud being due mainly to them, together with some species of desmids and dinoflagellates.

From an analysis of previous records of E. nordmanni, considered in conjunction with those furnished by the present investigation, the following points of interest emerge.

1. E. nordmanni, while being generally distributed in the North Sea and adjacent waters throughout the summer months, has been shown to breed freely in inshore waters in early summer and again in autumn when maximum numbers of individuals are obtained.

2. These two periods of maximal abundance are produced as the result of successive parthenogenetic broods and alternate with periods of depression. This is indicated not only by the sexually-produced winter-egg, but also by a reduction in the number of embryos contained in the brood chamber and consequent change in body-shape. This serves to show that the supposedly distinct races, described as being characteristic of the North Sea and the Baltic, have no doubt been founded on material taken at different periods of the agamic phase.

In August, 1932, six specimens of this species were found on the gills of Trachurus [Caranx] trachurus taken at Plymouth. This is the first record of its occurrence in British waters.

A new species of Orthonectid, Rhopalura granosa from Heteranomia squamula L., is described. The female is fusiform, and about 190 to 230μ, long, and 55 to 75μ broad. The male is also fusiform, but less than half the size of the female, being only 87 to 95μ, long and 20μ broad. R. granosa is distinguished from all other known species of Rhopalura by the presence in the male of large refringent bodies in the anterior cone, and in the first row of cells of the second ring. The male of R. ophiocomce Giard, a species closely allied to R. granosa, has the refringent bodies in the cells of the second ring only.

1. 188 Shags and 27 Cormorants, which had been feeding around the shores of Cornwall and whose stomachs contained identifiable food organisms, have been examined.

2. The Shags were found to have been feeding principally upon Sand Eels (Ammodytes spp.), and other non-marketable fishes.

3. The proportion of flatfishes and other economic species which had been devoured by the Shags was negligible.

The sodium, potassium, calcium, magnesium and iron of a number of marine invertebrates have been determined and some of the findings are very briefly discussed.

The common winkle Littorina littorea contains 330–510 mg. of magnesium per 100 g. of live weight. All the organs appear to contain these high concentrations. Boiled specimens of whelks contained about 160 mg. of magnesium per 100 g.

We should like to thank the Director and Staff of the Laboratory of the Marine Biological Association for their assistance. R. A. McC. has held a part-time grant and H. L. S. a full time grant from the Medical Research Council during this work.

Of 198 specimens of Gammarus zaddachi collected in the Estuaries of the Rivers Earn and Tay four individuals had abnormal eyes. This is the first record of abnormal eyes in wild specimens of a Gammarus species, although Laboratory strains of G. chevreuxi have developed them.

The investigation described in this paper was carried out as part of the programme of the Water Pollution Research Board of the Department of Scientific and Industrial Research, and is published by permission of the Department. My thanks are due to Dr. E. J. Allen and to Mrs. E. W. Sexton for their assistance in preparing the paper.

When examining the gills of a lobster for specimens of Nicothoe large numbers of copepods were found which, colourless and slender in form, had the sluggish and rather aimless movements which one would expect from a commensal removed from its natural habitat. It was somewhat of a surprise to find that they all belonged to a species already described —Tisbe elongata A. Scott. Scott obtained a few specimens from mud collected on mussel beds between Heysham and Morecambe. It appears, then, that we have here a species which is capable of free life, but its abundance, in all stages of growth, in the gill chamber of a lobster, proves that it is also to be considered a semi-parasite.

The Plymouth Laboratory is well situated for the study of the herring, and its commercial fishery, and since the winter of 1924–25, advantage has been taken of the varied facilities for research thus afforded. From time to time reports have been published in the Journal of the Marine Biological Association as a series, entitled: “Herring Investigations at Plymouth” and these have dealt with many seemingly distinct subjects of study, including experiments with larvæ from laboratory-fertilised eggs; studies of growth, migration and structure of young and old fish; and accounts of the commercial operations during the winter drift-fishery at Plymouth. It has now been considered advisable to bring together the several results in one paper, in an endeavour to show their essential bearing upon the problems of the practical fishery.

1. The most noticeable response of marine plankton to light, under laboratory conditions, is the formation of groups on the lighted (or opposite) side of the vessel containing them.

2. Specimens from such groups were tested under different conditions of illumination, and in all cases they moved in the direction of the light quite irrespective of accompanying changes of intensity in the surroundings.

3. Groups form around the line of direction of the light, or the resultant direction when the light is scattered or falling from more directions than one, this being the direct result of individuals moving along the mean path of incidence of the light.

4. The behaviour of individuals was examined more closely to distinguish between the two possible ways in which the directed movement could have been brought about, viz. (i) reactions to bilateral inequalities of illumination (here called “true topotaxis”), and (ii) reactions to changes in total illumination of light-receptors (a type of “phobotaxis”). For a number of species it was clearly a case of “true topotaxis,” and very probably for at least the majority of the rest.

5. In two very different cases, namely, Acartia clausi and Poecilochaetus serpens, there was no orientation of the body, but nevertheless efficient orientation of the path of movement. It is believed that this is the first occasion on which such behaviour has been described.

6. The observations described point to the fact that movement in the direction of incidence of the light, however this may be affected, is general among a wide range of the smaller, free-living, bilaterally symmetrical, marine animals, and would tend to dominate other possible response to light. This behaviour on the part of individuals provides a substantial basis for attempted explanations of the correlations, that have been demonstrated by ecological workers, between the vertical distribution of populations and light-intensity.