194 THE ROCK DOG-FISH. 



This fish is plentiful on the northern coasts of Europe, and is often thought a great 

 nuisance by fishermen, whose bait it takes instead of the more valuable fish for which the 

 hook was set. It generally remains near the bottom of the water, and is a voracious creature, 

 feeding upon crustaceans and small fish. It often follows the shoals of migrating fish, and on 

 account of that custom is called the Dog-fish. 



Generally its flesh is neglected, but when properly dressed it is by no means unpal- 

 atable, and is said to be sometimes trimmed and dressed in fraudulent imitation of more 

 valuable fish. 



The skin of this and other similar species is rough and file-like, and is employed for many 

 purposes. The handles of swords, where a firm hold is required, are sometimes bound with 

 this substance ; and joiners use it in polishing the surface of fine woods so as to bring out the 

 grain. It is also employed instead of sand-paper upon match boxes. 



The egg of this species is very curious in form and structure, and is often found on the 

 sea-shore, flung up by the waves, especially after a storm. These objects are familiar to all 

 observant wanderers by the sea-shore, under the name of mermaid's purses, sailor's purses, or 

 sea purses. Their form is oblong with curved sides, and at each angle there is a long tendril- 

 like appendage, having a strong curl, and in form not unlike the tendrils of the vine. The 

 use of these appendages is to enable the egg to cling to the growing sea-weed at the bottom of 

 the ocean, and is to prevent it from being washed away by the tide. After a storm, however, 

 when the agitated waves have torn up the beds of marine wrack and other sea-weeds that 

 usually lie in still calmness beneath their sheltering waters, and especially during the time of 

 low tide, these objects may be found lying upon the uncovered and dripping shore, their 

 strong but delicate tendrils entwined in almost inextricable complexity among the salt-loving 

 vegetation of the ocean, and their tiny inmates as yet imperfect and unborn. 



Water, which to these creatures contains the breath of life, gains access to the imprisoned 

 sharkling through two slight, longitudinal apertures, one towards each end of the egg ; and it 

 is a very remarkable fact that in these waters the undeveloped young are furnished with small 

 external gills, which are afterwards absorbed into the system a phenomenon curiously anal- 

 ogous to the structure of the tadpole. 



The substance of the egg-shell, if such a term can be applied to the envelope which con- 

 tains the young, is of a moderately stiff, horny character, becoming harder when dry, and of 

 a semi-transparent, yellowish hue, not very unlike, though not so clear as the yellow portions 

 of tortoise-shell. 



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 effectually 

 bars the entrance against any external foe. When it first leaves its horny home, the neophyte 

 Shark bears with it a capsule, containing a portion of the nutrimental principle of the egg, as 

 is seen in the chicken of the common fowl, and is enabled to exist upon this substance until it 

 has attained the power of foraging for itself, when the small remainder of the capsule is 

 absorbed into the abdomen. 



The head of the Little Dog-fish is rather flat upon the top, there is a little spiracle or 

 blow-hole behind each eye, and the shape of the mouth is somewhat like a horse-shoe. 



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 is about eighteen inches. 



THE ROOK DOG-FISH derives its name from the fact that it is often found on rocky coasts. 

 From its superior size, it is also known by the name of LARGE SPOTTED DOG-FISH, and on 

 several coasts it goes by the curt and not euphonious name of BOUNCE. 



The habits of this fish are so like those of the preceding species, that they need no 

 description. 



It may readily be distinguished from the little dog-fish by the large size and fewer number 

 of the spots, as well as by the shape of the ventral fins, which in this species are nearly squared 



