IN the waters off Plymouth there exists a definite inshore fishing-ground, approximately 13 square miles in area, locally known as the “corner.” In order to obtain some idea of the Bionomic conditions prevailing on this ground an intensive study of the bottom fauna was undertaken. Quantitative seasonal observations extending over a period of one year (August, 1928–July, 1929 inclusive) have been made, using the 0.1 square metre Bottom Sampler and the “Agassiz” Trawl, a method having been devised for obtaining quantitative hauls with the latter instrument. Investigations into the food actually eaten by the fishes within the area have been carried on simultaneously, and the stomach contents of over 2000 fishes comprising 29 different species have been examined. On account of the length of time required for stomach examination, it was found impossible to make seasonal observations on them also, but comparable winter and summer examinations were made.

A large number of collections were made with the 2-metre stramin ring-trawl in the years 1924, 1925 and 1926, to study the vertical distribution of young fish. Seeing that all these collections were made in exactly the same way, it was considered that they would form a good basis for a study of the quantitative differences in abundance of the different species at various times of the year. Accordingly, after 1926 the collections were supplemented in-1927, 1928 and 1929 by oblique hauls with the ring-trawl fishing at the same depths as those fished in the serial hauls in the study of the vertical distribution, that is the net was fished successively at the six different depths during half-an-hour's haul for 5 minutes at each depth. The results given in this report are all based on daylight catches.

Investigations concerning the main events in the transformation of the transparent eel-shaped larval herring into the silvery and scaled adolescent fish may proceed along two lines. In the first place, information may be sought as to the biological processes which bring about each event. For example, attention may be directed to the study of the differential growth of the body by which the form of the adult is attained; or, to the manner in which the scales are developed. But, secondly, it is of vital importance to learn how much the events of metamorphosis are affected by circumstances of time and place. Thus, at Plymouth, as elsewhere, we need to know the extent of possible differences in form and size between young fishes which have metamorphosed from larvæ born at different times.

According to E. T. Browne, 1899, Stephanomia bijuga (Delle Chiaje) (syn. Cupulita sarsii Haeckel and Agalmopsis elegans Sars, partim) belongs to the surface Atlantic fauna. It has been recorded at Valencia from March to November, and while suffering badly from the destructive power of gales it must occur at times in enormous numbers, for in November, 1898, tow-nets were taken that were full of isolated pneumato-phores. Into the more confined waters of the English Channel, however, it penetrates apparently very rarely, the only record being that of a single specimen taken a mile or two out from Plymouth Sound in March, 1902.

This apparatus was elaborated during some preliminary observations on the biology of the polychæte worm Melinna adriatica, and in view of its possibilities for facilitating observations on other small marine organisms, an account of it seems desirable.

The Amphipod corophium volutator Pallas has been descrobed, mainly from a purely systematic standpoint, under the synonyms C. grossipes Linnæus, C. longicorne Latreille, and G. bicaudatum Linneo (Delia Valle). Stebbing in his standard work (19) on the Gammaridea, accepts volutator as the earliest, and modern French and Danish authors follow him.

The temperature of the sea and the movements of water carrying with it planktonic organisms have been the subject of study since the early days of marine biological research. As investigation of cold-blooded marine animals progresses, the controlling r61e played by the temperature of the surrounding water upon their breeding, rate of growth, and general metabolism, becomes increasingly evident.

In the previous numbers of this series (1923, 1925, 1926, 1928) it was fully established that the phosphate and silicate content of sea-water becomes greatly reduced in spring and summer. It is possible to calculate a minimum value for the phytoplankton crop from the amount of phosphate used up, also to ascertain the production up to and between various dates; such information has a direct bearing on the supply of food for copepods and other animals upon which young fish feed. The accumulation of data of this type should in time permit of some generalization as to the favourableness or otherwise of any season with respect to the survival of relatively large numbers of young fish of various species in the locality studied. The present paper is a further contribution towards the amassing of seasonal productivity data which has been in progress since March 1923, with a gap from March to October, inclusive, during 1927. Information has moreover been sought as to the extent to which the removal of the phosphate approaches completion; the analyses of water samples low in phosphate have been carried out with a rather greater degree of accuracy than heretofore, by using a more exact method of allowing for the reagent blank, by using weaker standard solutions and by ensuring that in nearly every case the analyses were performed on the day following that on which the water samples had been taken. When the cruise extended for two days this was not possible as regards samples taken on the first day. Furthermore, measurements have been made (Poole and Atkins, 1928) of the illumination, both aerial and submarine, obtaining when the samples were taken.

The spring diatom increase in the open sea and probably also in inshore waters is one of the most important annual biological events and information regarding it or its causes is likely to be of value. In an inshore area changes are not only more pronounced, but also take place more rapidly than in the open sea and, for this reason among others, the increase was studied in Loch Striven, a well-sheltered loch in the Clyde Sea Area. A general description of the weekly changes occurring in this loch has already been made (Marshall and. Orr, 1927). The changes during the spring, however, are so rapid that an examination at even closer intervals during this period was thought advisable. Such an examination was made in 1927 and 1928, the interval between successive visits being generally two days. The methods used were the same as those described in the above-mentioned paper.

The importance of bacterial action in the seas has long been recognised, but investigation in marine bacteriology lags behind that of corresponding terrestrial problems. Such general information about marine bacteria as is now available is derived mainly from bacteriological work of some decades ago. At that time the technique of the science was not fully developed, but at the present day it has become so specialised that it lies outside the province of the marine biologist, although he alone is able to appreciate the significance of bacteria in the general economy of the sea.

Very little work has as yet been done on the occurrence and distribution of marine lichens in the Plymouth district. The present investigation of the genus Lichina was undertaken at the suggestion of Dr. J. H. Orton, who, having noticed the two Lichina species at New Train Bay near Pad-stow, North Cornwall, thought it might be of interest to determine their distribution in the Plymouth area.

A Heavy percentage of the mussels obtained from various parts of the Fal Estuary, during October and November, 1927, had the gills in an exceedingly abnormal condition (31.8% among 1488 recorded). Occasional mussels from other localities (Padstow, Teignmouth, Yealm, Saltash) have been observed to have slightly abnormal gills, though perhaps in the majority of these the condition was due to the presence of a large female pea-crab, Pinnotheres pisum. In the Fal Estuary mussels the abnormal conditions were doubtless correlated with some factor in the environment, the percentage of pea-crabs in these being so low (4–8%) that their presence could have no relation to the abnormal condition of the gills.