NA rURE 



\yune 6, 1889 



colours of its own. Thus the cod is known by its four 

 somewhat regular black bands, the pigment on the haddock 

 being less defined, the whiting by its canary-yellowish 

 hue, the gurnard by its chrome-yellow, the ling by its 

 gamboge-yellow, the flounder by its yellow and black, and 



Fig. 3. — Flounder showing pigment in ovo. 



SO on. All these hues, however, become greatly modified 

 during subsequent development ; indeed, the pigment in 

 no group of vertebrates shows more remarkable changes 

 between the young and adult states than certain of our 

 food-fishes. Thus for instance the cod is characteristically 



,^^ 



Fig. 4. — Larval cod with black spots or bands. 



speckled in its tiny youth (Fig. 4), next it becomes more 

 or less uniformly tinted, then the pigment groups itself 

 somewhat irregularly on the sides (Fig. 5) ; thereafter it 

 is boldly tessellated, subsequently blotched with reddish- 



FiG. 5. — Aggregations of pigment in post-larval cod. 



brown, and finally in its adult condition it again puts on 

 more or less uniform tints. The ling shows a similar 

 series of transformations, the colours, however, differ- 

 ing in their arrangement, being marked with gamboge- 



FlG. 6.— Tessellated condition of young cod (spirit-preparation). 



yellow in its larval, slightly banded in its early post-larval 

 stage, then the body becomes more or less uniformly 

 tinted in its post-larval phase, and the little fish is furnished 

 with a pair of enormously developed and bright yellow 



Fig. 7. — Long-finned post-larval ling (enlarged). 



ventral fins (Fig. 7)— so different from the short ones of 

 the adult. It is next striped conspicuously when about 

 3 inches long (Fig. 8), thus affording a great contrast to 

 the tessellated condition of the young cod. In this stage 



an olive-brown band passes from the tip of the snout in a 

 line with the middle of the eye, straight backward to the 

 base of the caudal fin-rays. The pale ventral surface 

 bounds it inferiorly, while a dorsal stripe with a beautiful 

 opaline lustre runs from the tip of the snout, over the 

 upper part of each eye to the tail, on which it is opaque 

 white, thus giving the fish a characteristic appearance. 

 The dorsal line from the brain backward is distinguished 

 by a narrow edge of dull orange or pale olive, which 

 relieves the colours formerly mentioned, and the general 

 effect is varied by two black specks in the dorsals. When 

 it is double the length {i.e. 6 or 7 inches), a complete 



Fig. 8. — Young ling alout 3 inches long (in .spirit). 



change has taken place in its coloration (Fig. 9). Instead 

 of being striped, the fish is now boldly and irregularly 

 blotched— both dorsally and laterally, the region of the 

 white stripe being indicated by the pale and somewhat 

 scalloped area dividing the dorsal from the lateral blotches. 

 Fourteen or fifteen brownish blotches occur between the 

 pectorals and the base of the tail, and they are separated 

 by the whitish areas, which thus assume a reticulated 

 appearance, and both kinds of pigment invade the 

 dorsal fins. Other touches of dark pigment on the fins 

 and tail increase the complexity of the coloration at this 

 stage. 



Fig. 9.— Young ling in the barred stage (about half natural size). 



Again, some species, like the gurnard, have pigment 

 over the yolk-sac before they are hatched, others have 

 not. The dragonet in its post-larval (and pelagic) stage 

 has its ventral surface deeply tinted with black pigment, 

 whileintheadult (aground-loving fish) it is white. The St. 

 Andrews cross in the eye of the post-larval four-horned 

 Cottus (C qiiadricornis) is another remarkable feature 

 (Fig. 10). No more interesting or more novel field, 

 indeed, than this exists in the whole range of zoology ; but 

 the investigations need ships and boats, with expensive 

 appliances, as well as persevering work for several 

 seasons. We have only been able to open the field at 



Fig. 10. — Head oi Coitus qnadricornis, with St. Andrews cross in eyes. 



St. Andrews by the help of the Trawling Commission 

 under Lord Dalhousie, and subsequently by the aid of 

 the Fishery Board. It may be asked. Why is all this 

 remarkable variation in colour ? Just for the same 

 reason that the young tapirs and wild pigs are striped, or 

 the young red deer spotted — the adults in each case being 

 uniformly tinted. Such features indicate their genetic 

 relation with ancestral forms having these marks ; and, 

 moreover, in the struggle for existence, such variations in 

 tint conduce to the safety of the young. 



The view of Eimer that the markings in animals are 

 primitively longitudinal would not suit for many fishes, 



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