June 13, 1889] 



NATURE 



159 



size are better marked, viz. the distribution of dense 

 blackish pigment along the base of the dorsal fins ; and 

 it soon spreads downward over the sides. The first anal 

 iin assumes the character of the adult, and a minute 

 papilla indicates a barbel. Between the stage just 

 mentioned and a length of 28 mm. a decided change in 

 the dense dorsal pigment takes place, viz. a tendency to 

 form separate groups or touches (Fig. \ 6). These differ from 



ViG. 16. — Young whiting, with serrated dorsal pigment-band and parasitic 

 C/ia/i»ius. 



the cod in being confined to the dorsal region, though a few 

 bars occur at the base of the tail. The fish is also now 

 minutely flecked, all over the head, sides, snout, and fins 

 with black pigment, and its general outline approaches 

 that of the adult. It is at once distinguished from the 

 young cod by the shortness of the snout, irrespective of 

 the features already pointed out, by the coloration, and by 

 the shape of the first anal fin. 



The differentiation of the two species, viz. the cod and 

 the whiting, is very marked in spirit at the length of 

 34 mm. In the whiting the median dorsal fin is less 

 abruptly elevated than in the cod, and the first anals 

 diverge widely, the elongation of the latter being probably 

 connected with the abbreviation of the abdomen. The 

 body of the whiting is more plump and neatly rounded 

 than in the cod, which is flatter and has generally a more 

 prominent abdomen. The pigment-specks closely cover 

 the sides of the body in the whiting, as well as the mem- 

 branous webs of the dorsal fins, and are continued on the 

 head. The pigment at the base of the caudal rays is more 

 distinct in the whiting, and the lancet-like caudal termina- 

 tion of the body is longer in this species. The myotomes 

 are coarser in the cod, and the surface has little of the 

 dappled silvery sheen of the whiting. The chromato- 

 phores are larger in the cod, and are grouped in blotches 

 over the surface, with intermediate pale patches, and 

 the shoulder and head have much less pigment than in 

 the whiting. Both the pectoral and ventral fins of the 

 cod are shorter than those of the whiting. The snout in 

 the latter is shorter and broader as well as deeper, and 

 the short sub-mental papilla is in contrast with the long 

 barbel of the cod of the same length. The whiting, 

 produced from an egg of larger size, would appear to 

 attain a plump body and finished outline sooner than 

 the cod. 



The foregoing stages are very abundant in autumn in 

 the deep water off the Isle of May and the mouth of the 

 Forth, but they also appear west of Inchkeith in the 

 latter estuary. They are indeed more characteristic of 

 the former region, as far as present observations go, than- 

 of the shallow water of the open bays, such as St. 

 Andrews, though on reaching a somewhat larger size 

 they are quite common in the latter expanse. Both they 

 and the cod in these early stages are infested by a 

 Crustacean parasite (Chalinius), which adheres to various 

 parts of the head and body, just as the larval Anceus 

 tenaciously attacks the young flounders in tidal harbours 

 and inshore grounds. 



The young whiting at a later stage (3 to 5 inches) joins 

 the young cod at the margins of the rocks, and forms 

 independent shoals in tidal harbours, as well as occurs 

 some distance off shore, being frequently got in the 

 mid-water net in the deeper water. Towards the latter 

 size (6 to 7 inches) it readily takes the hooks of the liner, and 

 in certain bays the multitudes of young whiting prove an 

 inconvenience to the fishermen. As it increases in size 



great shoals are formed in the offing, though a few small 

 are almost always found in inshore waters. 



The young round fishes, such as cod, haddock, and 

 whiting, of similar or nearly similar size, seem respectively 

 to herd together. Thus it happens that in certain hauls 

 of both liners and trawlers the majority agree in size. 

 This is well known to the liners, who in former days 

 specially sought out the young cod as already indicated. 

 The same feature is observed in many other fishes, and 

 probably conduces to their safety. 



So far as known, the adult fishes of the three kinds 

 specially alluded to in the preceding paragraph (viz. cod, 

 haddock, and whiting) follow no very definite law in 

 regard to migrations, if we except the apparent congrega- 

 tion in certain regions during the spawning season, as 

 pointed out, for instance, by Sars, off Lofoten, where they 

 occur in vast numbers from January to March. In our 

 own country, again, the appearance of shoals of haddocks 

 and whiting in certain localities is another example. 

 How far such multitudes, however, are influenced by the 

 abundance of food is still an open question. In British 

 seas the herring is the main cause of these congregations 

 in the cod and haddock ; the former chiefly pursuing the 

 fishes, the latter their eggs. In the same way, the 

 abundance of Norway lobsters and similar food on the 

 grounds called banks exercise considerable influence on 

 the presence of cod. 



It has already been pointed out, however, that in their 

 young stages certain migrations do occur. Thus the post- 

 larval cod by and by seeks the Laminarian region, while 

 the older forms for the most part tend to go seaward. 

 The same occurs even in a more pronounced manner with 

 the ling, the adults of which as a rule are found in deep 

 water. The pelagic post-larval ling seeks downwards as 

 it grows, and is seldom found near the shore till it attains 

 the length of 6 or 7 inches — in short, until it is barred 

 with pigment. As it increases in size it migrates seaward. 

 Similar features are noticed in the plaice. As observed in 

 the trawling expeditions of 1884, only large plaice as a rule 

 are procured in deep water off the east coast, while the 

 sandybays abound with those ranging from 1 1 inches down- 

 ward, and none of the females of which appear to be mature. 

 Multitudes of little plaice haunt the margins of these sandy 

 beaches, but it cannot be said that forms which have the 

 length, for example, of 3 inches, are confined to any 

 particular line drawn across a bay, for small forms (2 to 4 

 inches) occur in hauls all over such a bay as that of St. 

 Andrews. Small turbot and halibut in the same way are 

 often found in the shallow bays, while the large adults are 

 inhabitants of the deeper water. Such would not, however, 

 seem to be the case with certain skate, very large adults 

 of which occur in the shallow water of the sandy voes in 

 Shetland. 



On the other hand, the witch {Plciironedes cynoglossiis) 

 keeps to its special areas, both as regards the young and 

 the adult condition, so that the movements of eggs, larval 

 and post-larval forms are circumscribed ; and the same 

 would seem to be the case with the topknot {Zeugopteriis) 

 and sail-fluke [Arnoglossus). The dab {Pleuronectes lim- 

 anda), again, is found in all stages both in comparatively 

 deep and comparatively shallow water. 



Almost all our valuable food-fishes, therefore, are 

 produced from minute pelagic eggs, the enormous numbers 

 of which provide for a vast increase and wide distribution 

 of the species ; yet it cannot be said that this habit alone 

 provides for their multiplication when the case of the 

 herring with its demersal eggs, fixed firmly to the bottom, 

 is considered. It has to be borne in mind, however, that 

 the larval herring immediately mounts upward toward the 

 surface as soon as its strength suffices. 



Many striking changes occur during growth, both in 

 external form and coloration, but it is difficult at present 

 to lay down any general law that would apply to all cases, 

 though those in which certain migrations take place 



