1889/ 



on the Life-Jiistory of a Marine Food-fish. 



391 



whitish areas, which thus assume a reticulated appearance, and both 

 kinds of pigment invade the dorsal fins. Other touches of dark 



Fig. 9 



' WS 'M "w 'i'^^n ^^- ~^fe^~J^ 



:: ^;.^^%V^-.X^ >.\^^. NXNXXX-^. ^.^ ■ 



Young Ling in the barred stage. About half natural size. 



Fig. 10. 



pigment on the fins and tail increase the complexity of the colora- 

 tion at this stage. 



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, while in the adult, a ground-loving fish, 

 it is white. The St. Andrew's cross in the eye of the post-larval 

 four-horned Cottus (0. quadricornis) 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 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 varia- 

 tion 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, more- 

 over, 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 primi- 

 tively longitudinal would not suit for many fishes, notably for the 

 young cod, ling, and Pleuronectids, and, indeed, Haacke has already 

 pointed this out from a study of the Australian fish, Helotes scotus* 

 the adult of which is marked by eight longitudinal bands, while 



Head of Cottus quadricorni with 

 St. Andrew's cross in eyes. 



One of the Pristipomatidae. 



