THE DOG-FISH. 



535 



is to enable the egg to cling to the growing seaweed at the bottom of 

 the ocean, and to prevent it from being washed away by the tide. 



For the escape of the young shark, when strong enough to make its 

 own way in the wider world of waters, an outlet is provided in the 

 opened end of the envelope, which opens when pushed from within, 

 and permits the little creature to make its way out, though it effectual- 

 ly bars the entrance against any external foe. 



The head of the Little Dog-fish is rather fiat upon the top, there is a 

 little.spiracle or blow-hole behind each eye, and the shape of the mouth 

 is somewhat like that of a horseshoe. The general color of the body is 

 pale reddish on the upper parts, covered with many little spots of dark 

 reddish brown ; below it is yellowish white. The length of this species 



The Dog-fish {ScyUium caniculum). 



is about eighteen inches. The color is beautiful slate-blue above, and 

 white below. 



The remarkable fish depicted in the illustration affords a striking in- 

 stance of the wild and wondrous modifications of form assumed by cer- 

 tain creatures without any ascertained purpose being gained thereby. 

 We know by analogous reasoning that some wise purpose is served by 

 this astonishing variation in form, but as far as is yet known there is 

 nothing in the habits of this species that accounts for the necessity of 

 this strange shape. 



The shape of the body is not unlike that of the generality of sharks, 

 but it is upon the head that the attention is at once riveted. As may 

 be seen from the figure the head is expanded laterally in a most singu- 

 lar manner, bearing, indeed, no small resemblance to the head of a 



