1889.] 



on the Life-history of a Marine Food-Jish. 



395 



ground-fish) tliey attain no greater dimensions than in the cod, both 

 having at a certain stage soft, free filaments or tactile processes at 

 the tip. The ventral fins in the post-larval rockling are equally large, 

 the distal half being black, so that at first sight the little fish when 

 captured seems to possess a great ventral spine on each side (Fig. 12). 



Fig. 12. 



Post-larval Rockling, enlarged. 



In the post-larval gurnard, again, the huge pectoral fins form a 

 drapery for the entire body when folded back, only the tip of the 

 tail extending beyond them (Fig. 13). They are indeed proportion- 

 ally as large as in the southern flying gurnards, but in these the 

 fins reach full develojDment only in adult life, while in the young 

 stages they are comparatively small — exactly the reverse happening 

 in the grey gurnard of our seas. The presence of the broad arches of 



Fig. 13.- 



Post-larval Gurnard, enlarged. 



pigment on the pectorals of several forms, such as the present species, 

 green cod, and armed bullhead, is also an interesting feature. We 

 have not yet read the riddle of all these changes, but in the ling the 

 great ventral fins are probably connected with its roaming or pelagic 

 life, and this explanation would also suit in the case of the rockling, 

 both in their mature state seeking their food on the ground. 



The little fishes at this stage are still more or less translucent, 

 except in the region of the eyes, which are silvery, and on the parts 

 where the pigment occurs. Moreover, their fondness for a minute 

 reddish Copepod (^Calanus finmarcliiciis), which occurs in myriads 

 around them, gives the region of the stomach a faint j)inkish hue from 

 the translucency of the tissues. By-and-by, however, pigment apj)ears, 

 foreshadowing in the cod (Fig. 5) those peculiar squares which give the 

 sides, at a somewhat later stage, their tessellated or tartan-like aspect. 

 Besides, they are found nearer the bottom of the water, so that they can 

 be captured in a naturalist's trawl with a fine gauze bag at the end. 

 There is, therefore, a downward tendency as the little fishes get older 



Vol. XII. (No. 83.) 2 b 



