57^ 



NA TURE 



{Oct. 9, i8?4- 



SCOTTISH FISHERY RESEARCHES 



A TPENDIX F of the Report of the Scottish Fishery 

 -'""*• Board contains a series of valuable papers with accu- 

 rate and well executed plates. Dr. Stirling gives a pre- 

 liminary report on " The Chemistry and Histology of the 

 Digestive Organs of Fishes." The first part gives the results of 

 chemical investigations of the digestive processes in the herring, 

 cod, haddock, and skate. The second part deals exclusively 

 with the intestinal tract of the herring. The muscular coat of 

 the oesophagus consists of striped muscular fibres arranged mi ire 

 or less regularly at the upper part, but disposed circularly in 

 several layers at the lower. The mucous membrane of the 

 oesophagus has longitudinal folds, and is lined with cylindrical 

 epithelium interspersed with numerous goblet cells. The oeso- 

 phageal glands are simple tubular glands, with, at first, a very 

 short secreting portion. The glands in the "cardiac sac," or 

 "crop," are, like those of the oesophagus, branched tubular 

 glands lined in their upper part by tall columnar epithelium, and 

 in their secretory parts by a single layer of cubical cells, like the 

 "outer" cells of the fundus in mammals. The gland tubes 

 become shorter towards the lower part of the cardiac sac, and 

 they are absent in the pneumatic duct, which is lined by a single 

 layer of columnar epithelium, and divided into two compartments 

 by folds of the mucous membrane. Dr. Stirling has found that 

 the organ which has been hitherto known as the "crop "in 

 the herring, is something more than a mere receptacle, and 

 corresponds in structure and function to the cardiac portion of 

 the stomach of higher vertebrates. There is a striking resem- 

 blance between the cells lining the secretory portion of the gland 

 tubes and the "outer cells" in the mammalian stomach, the 

 point of difference being that the tubes are lined by a single 

 continuous layer of these cells. There are apparently no internal 

 layers of cells comparable to the inner cells of mammals, and, as 

 might be perhaps expected, the glands are simpler than those of 

 the mammals, and without that differentiation of tissue which is 

 brought about by specialisation of function. One cell may sub- 

 serve two functions, and, from an evolutionist's point of view, 

 the secretion of an acid and the formation of a ferment 

 have not as yet in the fishes been relegated to two distinct 

 sets of cells. The pyloric sac or stomach is that short tubular 

 organ with thick muscular walls, and resembling a gizzard, 

 which opens out of the crop and is continued into the in- 

 testine. The surface of the mucous membrane consists of 

 irregular depressions, which are deeper than those of the cardiac 

 sac and may be regarded as crypts. The pyloric sac is always 

 lined by a very thick coating of mucus, which not only lies on 

 the surface, but dips down into the pyloric crypts. Thesurface 

 of the pyloric sac and the glands or crypts are lined throughout 

 with a single layer of tall, narrow, columnar epithelium, having 

 the same character as that which lines the gland ducts and the 

 surface of the cardiac sac. There is no muscularis mucosa;. 

 The circular muscular coat is very thick, while the longitudinal 

 is thin. Structurally the pyloric sac is comparable to the pyloric 

 end of the mammalian stomach. Plates i. and ii. give series 

 of figures illustrating various points in the anatomy of the 

 intestinal part of the herring. 



Prof. Macintosh gives a short note of preliminary observations 

 made at the Marine Station, St. Andrew's, on the ova of various 

 food fishes. Cod ova were specially examined, and exp 

 made as to their buoyancy and the effects of impure water, 

 which proved very marked, and of changes of temperature. The 

 small size of the yolk-sac, as well as the activity shown from 

 the first by the newly-hatched fish show that they must soon 

 take in nourishment from without. The ova of the common 

 flounder were successfully hatched out. Other forms examined 

 and experimented on were the long rough dab, turbot, Cyelo- 

 plerus lumpus, herring, &c., and amongst invertebrates the ova 

 of squids, Natica, whelk, nudibranchs, mussel, Astenas rubtns, 

 lobster, and shore-crab. 



The vexed question as to whether the sprat is a separate species 

 of the Clupeicte or merely the young of the herring is satisfac- 

 torily settled in favour of the former opinion in the first part of 

 the Report on the Sprat Fishing during the Winter of 1SS3-84, 

 by J. Matthews Duncan, F.R.S.E., in which definitions of the 

 differences in external and internal characters are distinctly 

 proved. The sprat is more graceful in shape and slightly thicker 

 in body than the young herring. The dorsal surface of the head 

 is proportionally slightly longer in the herring, the operculum 

 therefore extending further back. The suboperculum in the 



sprat is shorter and more triangular. The lower jaw is alwa\ ■- 

 longer and the diameter of the eye rather larger in the herring. 

 In both sprat and herring the lower edge of the belly from tl e 

 anal fin forwards is covered by a series of scales, having a central 

 longitudinal "keel" and two lateral rays projecting forwards 

 and upwards. These are more numerous but weaker in the 

 herring than in the sprat, where the central keel is stronger and 

 the termination forms a sharp point, so that the difference can 

 easily be felt. In the sprat the pelvic fin is anterior to the first 

 ray of the dorsal, whilst in the herring it is posterior to it. The 

 pectoral fin is placed proportionately further back in the 

 herring, and the centre of the dorsal slightly behind the centre 

 of the body. The position of the dorsal fin varies more in the 

 sprat, the position of the anal fin more in the herring. The 

 number of rays in the pectoral, dorsal, and anal fins is not con- 

 stant in either species, but appears invariable in the pelvic fin, 

 that of the herring having two rays more. The arrangement of 

 the teeth in both species is the same on the maxillae, premaxilke, 

 and tongue, but those on the tongue are smaller in the sprat, 

 and the vomerine teeth present in the herring are entirely 

 wanting. The same superiority, as far as number is concerned, 

 shown by the herring in the fin rays, scales, &c. , is seen in com- 

 parison of other organs, the vertebrae, gill-rakers, and filaments, 

 the branchial and pseudo-branchial filaments, and the branchio- 

 stegal rays, being all more numerous than in the sprat. The 

 pyloric caeca are also more numerous. The slender duct by 

 which the stomach (crop of Huxley, Nature, vol. xxiii. p. 607) 

 communicates posteriorly with the swim-bladder is slightly 

 shorter and thicker in the sprat. In the herring the anterior 

 end of the swim-bladder gives off two delicate branches, which 

 run forward at first along each side of the parasphenoid, then 

 diverge, and enter a small spindle-shaped capsule. From the 

 anterior end of this capsule the duct passes out, and divides into 

 two lianches, one of which runs straight forward from the vesicle, 

 whilst the other passes outwards at nearly a right angle. In the 

 herring the ducts are very delicate tubes, measuring, in aliening 

 120 mm. long, o'9 mm. in diameter, and are surrounded by a cat ti 

 laginous sheath, "25 mm. in external diameter. The ducts meet 

 posteriorly in the middle line, and open by a single aperture into 

 the narrow anterior end of the swim-bladder. The spindle- 

 shaped capsule is about 1 mm. long by '6 mm. broad, and the 

 spherical capsules are about I '3 mm. in diameter, the anterior 

 one slightly larger. The sprat, however, shows a remarkable 

 departure from this arrangement. The ducts are about the same 

 size as, and their form and direction are similar to, those in the 

 young herring, though, at the point where they diverge from 

 the parasphenoid (about 5 mm. from the swim-bladder) they lie 

 higher, and are more difficult to follow. But the duct on each 

 side ends in a single capsule only, exactly similar to that of the 

 herring, and it neither forms a spindle-shaped dilatation, nor 

 gives off a branch to a second vesicle. Thus, while in the herring 

 there are three vesicles on each side of the head, all containing 

 air, in the sprat there is only one. The foregoing differences 

 are so numerous and so constant at all seasons that there can be 

 no question as to the sprat being a distinct species from the 

 herring, a further proof being that the former is found with de- 

 veloped milt and roe. Mr. Matthews shows in Plate iii. the 

 difference between sprat and herring in the shape of the body 

 and the keel scales, in the size of the ova, and in the formation 

 of the air-vesicles oi the ear. 



In the valuable paper on the " Natural History of the 

 Herring" Prof. Cossar Ewart, Convener of the Scientific Com- 

 mittee, treats of the varieties of the herring, the migration, the 

 spawning-ground, the process of spawning, and the artificial 

 fertilisation and hatching of ova. The varieties of the herring 

 have long been discussed in all countries frequented by this fish, 

 and differences believed to exist not only between herring of 

 different countries, but of different districts and seasons. How 

 far this may be true could not be determined even by careful 

 examination and figuring of over 500 specimens, taken at 

 different parts of the coast during winter and spring. Compari- 

 sons of outline show not so much that the herring of one district 

 differ from those of another, but that there is a remarkable 

 variation amongst herring caught at the same time. Heincke 

 (" Varietaten d. Herings. Jahrb. d. Comm. in Keil, 1876-78") 

 considers the position of the dorsal and pelvic fins of great im- 

 portance, but, as specimens examined of the same length, 

 caught at the same place, and as nearly as possible at the same 

 stage of maturity, showed more difference than Heincke finds in 

 his autumn and spring herring, some better character must be 



