A meter is described which measures the volume of water which has passed through a silk net which may be either towed or lowered and raised vertically.

A double release gear and throttling arrangement allows the net to be opened and, later, closed at any desired depths.

The catch of phytoplankton, from a volume of water which has been measured by the meter, may be assessed from its content of yellow-green pigments, which readily dissolve in acetone.

A rapid method of measuring the pigment content of the catch in terms of arbitrary units of plant pigment is described. The arbitrary unit is related to numbers of two species of diatoms.

The irregular distribution of phytoplankton in the sea is considered in connexion with representative sampling with this measuring net.

Vertical hauls were made with a very fine silk net having a meter attached, which measured the volume of water filtered, at positions off Plymouth throughout the year 1933.

The quantity of phytoplankton was assessed from its content of yellowgreen colouring matter, and expressed in terms of “units of plant pigments” per cubic metre of water filtered.

The diatom population per cubic metre at Station L4 on March 28th was estimated to contain phosphorus amounting to 2 mg. P2O5, whereas dissolved phosphate amounting to some 15 mg. P2O5 had been used from each cubic metre of water by the diatoms during the previous six weeks.

It is concluded that the production of phytoplankton during this period greatly exceeded the quantity found at the height of the spring outburst, and that the excess had been eaten by the herbivorous zooplankton.

1. The seasonal changes in the population of Calanus in Loch Striven in 1933 have been investigated.

2. There were three main breeding periods. The first was in February and March, an unsuccessful beginning of the second in April, the true second brood in May to June, the third in July, and subsidiary broods in August and September.

3. Numbers were very low until April when the copepodites of the first brood caused a large increase; there was a second increase in May consisting mainly of the eggs of the second brood, and the maximum for the year came in July. The last and subsidiary broods provided the stock for the autumn and winter of 1933.

The swimming methods and habits of certain Decapod larvse have been observed. The first larva of Munida bamffica was chosen for special attention. Such a study shows the importance of (1) orientation, (2) the presence of a reversal mechanism.

Observations on other types show these factors to be of great importance and also show that there are a great variety of attitudes in which larvæ swim.

Points in the relation of the larvæ to their environment were next considered; orientation is again important here, but whereas in Munida larvæ a “resting” orientation is found no such attitude is seen in Brachyurous zoeas.

1. The volumes of Balanus balanoides, at three levels of the shore, have been observed for a year.

2. The young barnacles grow very much faster than older ones.

3. The growth rate varies greatly with age, season and tidal level, but in general there is a period of maximum growth in the summer, and very little growth in the winter.

4. Growth, except during the first year, is greatest higher up the shore.

5. Young barnacles, which settle too late in the year, have their growth retarded by the summer heat, but almost catch up in size the earlier settled spat, by the beginning of the next year.

6. The growth rates found are intermediate between those recorded from Herdla (near Bergen), and those from near St. Malo.

7. Most of the lower- and middle-zone barnacles die in their third year, but those from the extreme top zone may live for five years or more.

There are two types of ground at Port Erin, differing widely in the general environmental conditions, and each with a characteristic type of urchin on it. The difference is sufficiently well marked for the local fishermen, who collect the urchins for sale to summer visitors, to distinguish them as different types. The littoral urchins from the Breakwater are larger and thicker shelled than those from the Breast. Their gonads reach a greater maximum size, and, in fact, never fall as low even as the maximum volume for the Breast urchin gonads. This difference is probably correlated with the much greater food supply on the Breakwater, since the gonad is the one organ of the body in which the animal can store reserve food material. Spawning commences in March or April and lasts for about two months, but is slightly earlier on the Breakwater than on the Breast. Ripening also takes place considerably earlier in both sexes on the littoral ground. Spawning seems to set in at a temperature of about 7° C., and the colder winter of 1931, compared with 1932, was associated with a later ripening and spawning, i n the former year. Similarly it is suggested that the slightly later spawning on the Breast than on the Breakwater is correlated with the slightly later rise in the temperature of the water on the deeper water ground in the spring.

In the course of work on the life-history and biology of the Raiidæ in the English Channel, and especially of R. clavata, the most important species commercially (4, p. 9 et seq.), it has been found necessary to attempt to disentangle the migrations of sexually mature fishes from those of juvenile individuals by means of marking experiments. In both sexes sufficiently small individuals could with safety be written down as juveniles and the largest of both sexes as adults. There remained, however, a considerable but ill-defined range of sizes (different in the two sexes) within which might be found fishes of all stages—juveniles, adolescents and adults.

1. A special study has been made of a small Metridiuni-like anemone found at Dingle, Liverpool, in comparison with the typical form of Metridium senile (L.) var. dianthus (Ellis).

2. Penicilli, formerly believed to be absent from the acontia of typical M. senile, have been discovered in abundance in the young, but rarely in the adults. In young and sexually mature specimens of the Dingle anemone they are also abundant.

3. There is close agreement between the anatomy of the Dingle form and the typical M. senile.

4. A considerable amount of variation occurs in the Dingle anemone, as in M. senile var. dianthus and M. marginatum, Mime-Edwards.

5. The resemblances and differences between the Dingle form and M. senile indicate that the former is a dwarf variety of the latter.

6. The discovery of an abundance of penicilli in the acontia of young typical M. senile and mature specimens of the Dingle variety, in conjunction with the great amount of variation in the genus Metridium, suggests that a reconsideration of the systematic position of the genus is necessary and would justify either the restriction of the family Metridiidæ to the single genus Metridium, or else the fusion of the Metridiidæ with the Sagartiidæ. The sum of the evidence appears to lie in favour of placing the genus in a family by itself.

A brief reference to the state of opinion concerning the water movements off S.W. England is made. Then a series of Drift Indicator records relating to 28 days of observation at 6 fathoms depth from the Seven Stones Lightvessel is presented and discussed. An overall flow of water towards the S.E. quadrant and of speed approaching 2 miles per day characterised the entire period. The residual current as worked out for the individual records, displayed considerable variation in speed and direction—setting as frequently towards the northern half of the compass as towards the southern, but more frequently towards the eastern half than towards the western half. There were pronounced changes in the wind speed and direction, and it appears as though the wind can drive the water at 6 fathoms depth towards a point to the right of its own direction, no matter from which of the four quadrants it blows.

Various attempts have been made to substitute certain elements for those acknowledged as essential for plant growth. Using plant material, sodium is the element usually chosen as a possible substitute for potassium, but results show that whilst sodium may be taken up in fairly considerable quantities this is only possible if small amounts of potassium be present as well. Total replacement appears to be impossible (11,13,15).