During the winter of 1927–28 the progress of the herring fishing at Plymouth was followed for the fourth consecutive season. A diary of market events was again kept by Mr. A. J. Smith of the Laboratory staff, while statistics of commercial landings and of the number of visiting drifters were kindly supplied by Mr. T. Edser of the Statistical Department, Ministry of Agriculture and Fisheries, and by Mr. E. C. Nelder of the Sutton Harbour Improvement Company, respectively. In the examination of age and growth of random samples of herrings, Mr. F. J. Warren, Laboratory Assistant, again acted as recorder. Details of the methods of treatment of the data collected will be found in Part I of this series of Reports (Ford, 1).

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.

As explained in Part I of this series of Reports (Ford, 1, p. 238) it was thought that the study of herrings landed at other ports would provide information bearing upon the question of the origin and migrations of the shoals visiting Plymouth during the winter. The examination of the appreciable number of such samples obtained, however, has yielded results which are of interest in themselves, apart from their application to the question of the Plymouth fishery. In this paper, an account is given of the study of herrings landed at Hastings and Brighton from off the Sussex coast, and at Brixham from the Great West Bay. It is necessary to point out that the sampling was not specifically designed for such a study, so that due allowance for this fact must be made in drawing conclusions as to the progress of the local fisheries.

Observations on breeding (1, 1914; 2, 3, 1920) and experiments on the rate of growth of marine invertebrates (4, 1914; 5 to 9) have been carried out since 1911 (excepting the war period).

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.

Mr. Leigh-Sharpe, in his account of the external structure of this interesting Copepod (1926), concludes that it is most nearly related to the Ascomyzontidæ. Having recently obtained a number of larvæ, hatched from adults obtained at Plymouth, and finding that my own conclusion as to the relationship of the genus differs from that of Mr. Leigh-Sharpe, it seems worth while to describe the larvæ and the bearing they seem to have upon the systematic position of the adult.

The larvæ hatch and become active inside the egg-sac. Immediately after becoming free they swim vigorously for a short time, but very soon sink to the bottom and remain quiescent, with occasional spasms of activity.

It has previously been shown (Ford, 1, p. 284) that herrings with fully ripened roes or milts form a considerable proportion of the landings by commercial drifters at Plymouth during December and January. Although naturally-deposited spawn has rarely been obtained from the sea-bottom in the district, the fact that newly-hatched larvæ occur in abundance provides evidence that actual spawning occurs locally. It has also been shown that from the end of September onwards, ripe fishes may be taken in stop-nets in Plymouth Sound, and even in sprat-seines in the estuarine waters of the River Tamar. A number of interesting and important questions is suggested by these observations. For example, do the ripe herrings which frequent the River Tamar actually spawn there, and if so, are they morphologically identical with those which spawn at sea, or are they of a different character? Would eggs deposited in the river be successfully fertilised and able to endure the periodic freshening of the water? Are the morphological characters of the offspring in any way dependent upon the environmental conditions under which they are developed?

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.

During a short stay at the Laboratory at Plymouth, with the object of studying the larvæ of Longipedia and Misophria, I was successful in identifying the nauplius of the former, and, as it is of rather exceptional interest from the systematic point of view, the various stages are described here. I did not find the adult of any species of Longipedia and am not able to describe the first nauplius with certainty, but the identity of the series as a whole was settled beyond doubt by the moulting of a late nauplius into a Copepodid which could be definitely identified as a species of Longipedia. It is impossible to say to which species it belonged, but the specific determination is not of serious importance.

From two series of samples of different populations of herrings from the neighbourhood of the Isle of Man, data were obtained of the lengths, weights, gonad-weights, and ages of 396 mature fishes. The growths of the whole body and of the gonads were represented by the upper portions of S-shaped curves. The male and female body-weights are nearly the same at any age over the range considered, but the testes of the male are always heavier than the ovaries of the female in such comparable fishes. The females attain a greater size than the males.

The weight of the gonads bears a linear relationship (as a first approximation) to the total weight of the fish over the range of size considered. The regression functions evaluated for the two sexes are

where y is the gonad-weight and x the total weight of the fish, both in grams. The difference between the weights of testes and ovaries in male and female fishes of the same size is therefore about 4·7 gm., which is shown to be significant. It cannot be due to specific gravity of growthrate differences, since the regression coefficient (0·26) is the same for both sexes.

It is suggested that the reproductive organs start to develop in the summer following the laying down of the first winter ring on the scales; and that the initial handicap in female gonad-weight may be due to the males being smaller than the females at this time.

Confirmation of the conclusions drawn from the Calf herring is given by a similar analysis of the Low herring samples.

That a mother worm protects its eggs until tie young are hatched is common enough among Polychætes, but not in the family Phyllodocidas.

McIntosh (1908) mentioned in his British Annelids, Vol. II, Pt. I, p. 49, that two female specimens of Notophyllum foliosum, procured by his late friend Dr. Howden, at Lamlash, Arran, in August, were laden with mature eggs. Certainly the words “were laden” used here tell us something about the particular habit of the worm, but the sentence is too short and is not emphatic enough to attract attention.

About 9a.m. (flood tide) on 17th August,1928, a large sailfish was captured in a dying condition in the main channel of the Yealm estuary, South Devon, opposite the Yealm Hotel, about a mile above the Yealm Bar. The fish was carefully packed up by Mr. V. C. Wynne-Edwards, and promptly despatched to the British Museum (Natural History), where the plaster-cast shown in the accompanying illustration (Fig. 1) was prepared by Mr. S. Stammwitz. The specimen was then cut into two pieces and preserved in alcohol.

Owing to the difficulty of preserving these large fishes in museums, except as stuffed skins, and to the marked changes which they appear to exhibit at different stages of growth, our knowledge of the group which includes the swordfishes, sailfishes, and spearfishes is decidedly limited, and the identification of species is a matter of some difficulty.

In a recent monograph, Jordan and Evermann distinguish nine species of Istiophorus, of which five are said to be new to science. The descriptions of four of these new species are based solely on photographs, the fifth being described from a plaster cast in the museum at Honolulu. As suggested by the authors themselves, some of the characters used by them in their key to the species may be “matters of age not indicating specific distinction.” According to this key, the present specimen from Devonshire would appear to be referable to one of their new species—I. maguirei from the West Indies, but, so far as I am able to judge from the description and photograph, there seems to be no valid reason for separating this from I. americanus, which is found on the Atlantic coast of America from Brazil northwards to Cape Cod and beyond.

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 facts of Polychæte embryology inform us that the change of the trochonphore into the perfect worm consists, first of all, in a growing out of the posterior section of its body and a gradual reduction of the anterior part, segmentation appearing at the same time. Thïs phenomenon depends upon a marked change of the mesodermal bands, situated on each side of the intestine. Each of them is separated into two cell-layers, which spread out toward the mid-ventral and mid-dorsal lines. Then a segmentation makes its appearance in them, proceeding from in front backwards, and almost simultaneously the two layers of the bands separate from each other, by the formation of a cavity in each section or segment. That new segments are gradually formed one after the other, and from before backwards, in the hinder part of the growing body, holds true universally, but, at the extreme end a segment has been individualised from the first, or at a very early phase of the segmentation, and this segment does not divide again even to the end of development. In this way the pygidium is formed, and it represents the posterior individual portion of the trochophore. The growth of Polychæte-larvæ is therefore anteanal and entirely in the penultimate segment.

A specimen of Galathea strigosa (L.) with a parasite of fairly large size at the abdomen was collected at the Looe-Eddystone Grounds near Plymouth on June 11th, 1913.

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 following is an account of a faunistic investigation covering those parts of the Rivers Tamar and Lynher which are affected by the tide, and was carried out during a period of six months from June to November, 1928.

Description of the Area.

The Tamar forms a portion of the boundary between Devon and Cornwall and flows in a southerly direction along a more or less winding course. (Chart.) The extent of the stream dealt with is from Plymouth Sound to Weir Head, some 19 miles inland measured along the water course. For about 6 miles downstream from Weir Head, the valley is rather narrow with rock exposures at different places on the convex side of bends, the water being confined to a well-defined channel with steep sides, which are uncovered by the vertical contraction of the stream at low water. The remainder of the river, down to the sea has, generally, a mud bank on each side, except at occasional bends where rock is present, which is exposed at low water by the lateral contraction due to reduction in level. The upper 4 miles of this region has narrower mud-banks than has the lower portion. These mud-banks or -flats are for the greater part more or less plane surfaces, which may slope gradually into the bed of the main channel, as happens in the lower portion of the area, or they may slope suddenly downwards at the edge, thus forming a well-marked bank to the main channel. In many cases their landward edges lie below high-water neap tide, but in others they slope imperceptibly into the adjoining land surface.

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.