58 LIFE-HISTORY AND DEVELOPMENT OF 



About this time the ventral fins of the pelagic fishes first 

 make their appearance, for hitherto they have managed to do 

 without them. Moreover, these fins in some, such as the 

 rockling and ling, undergo remarkable development, forming in 

 the latter (Fig. 6) a pair of great ventral wings conspicuously 

 coloured yellow ; yet in the adult (a ground-fish) they 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. Post-larval liockling, enlarged. 



(Fig. 12). In the post-larval gurnard again, the huge breast- 

 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 proportionally as large as in the southern flying 

 gurnards, but in these the fins reach full development only in 

 adult life, while in the young stages they are comparatively 

 small exactly the reverse happening in the grey gurnard of 



FIG. 13. Post-larval Gurnard, enlarged. 



our seas. The presence of the broad arches of pigment on the 

 breast-fins of several forms, such as the present species, the 

 green cod, and the 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 cases of the rockling and the armed bullhead, both, in 

 their mature state, seeking their food on the ground. 



