THE INFANCY OF FISHES 225 



short, the adult being excessively elongated, and flattened 

 from side to side. In the form of its fins, again, it is 

 totally different. And this is especially true of the back 

 fin and the breast fin. In the first named the foremost 

 of the fin rays, or supports of the fin, are prodigiously 

 elongated, attaining a length far exceeding that of the 

 body, and each ray is further provided with small flaps of 

 skin. The fin-rays of the breast fin are in like manner 

 elongated, and to the same excessive degree. What 

 purpose such fragile filaments serve we can only guess 

 at. Briefly it is believed that, like the adults, the larvae 

 are dwellers in the great deeps of the ocean, and that 

 these long rods and their flag-like appendages are highly 

 sensitive organs of touch. 



Equally puzzling is the stalk-eyed fish shown in our 

 illustration. This has been obtained once or twice ii. 

 deep-sea dredging, and is believed to be a larval fish. 

 Its most conspicuous feature, undoubtedly, is its eye, 

 which, it will be noticed, is mounted at the end of a long 

 stalk— a peculiarity shared by no other member of the 

 vertebrates. This stalk is apparently retractile, so that, 

 warned perchance by vibrations in the water of an 

 oncoming foe, the stalk can be suddenly shortened, the 

 eyes drawn down to the head, where it will be com- 

 paratively safe. But of what advantage can it be to the 

 larvae to have its eyes exposed to such constant peril ? 

 The only light they can ever perceive is the dim phos- 

 phorescent glow of the creatures around it ; for in the 

 abysses in which it lives the light of day can never penetrate. 

 Only among insects and crustacea and the snail do we 

 meet elsewhere with eyes mounted on stalks, and here, 

 save in the case of the snail, the stalks are inflexible. 

 Among fishes, it is true, we have an approach to this 

 15 



