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brought into a tank, it first swims rapidly about with beau- 

 tiful undulating motions of its silky body, but very soon grows 

 faint, and at last can no more rise from the ground, and re- 

 fuses all nourishment. The propagation of this fish is very in- 

 teresting, for it is one of the sharks that give birth to living 

 progeny. The embryo develops by means of a so-called yolk- 

 lag-placenta, that is, there are formed on the surface of the 

 yolk numerous little protuberances that fit into corresponding 

 depressions on the sides of the womb, and thus a connection 

 is maintained between the mother and the fruit similar to that 

 known in the mammalia. There has been frequent opportunity 

 in the Aquarium to witness the birth of from fifteen to twenty 

 young ones. 



Another fish that bears living young, and forms the transi- 

 tion from sharks to roaches, is the Sea-angel (Squatina an- 

 gelus); a large mishaped fish, which like the flat fish, lives 

 always on the ground , and is often taken for dead by the 

 spectator. The sea-angel is one of the dullest and laziest fish 

 in the Mediterranean, and feeds on what it finds living at the 

 bottom of the sea. When disturbed it swims pretty quickly, 

 end shows the wing-like shape of its pectoral fins, from which 

 it derives its name. Poor people eat its bad flesh, and its skin is 

 manufactured into rasps, knife-handles, sheaths, and such like. 



The real roaches have a flat body shaped like a plate and 

 all on one side. On the upper side, which is dark coloured, 

 are the eyes and two spouting holes that lead to the gills. 

 The long thin tail is usually spiny. They are all ground-fish, 

 and, like the sea-angel, live on the fish that inhabit the same 

 region. 



The most interesting variety is the electric ray (Torpedo), 

 the electric power of which was known to the ancients. Its 

 flat, naked, slimy body is nearly round, and contains on each 

 side a large bean-shaped electric organ, consisting in numerous 

 vertical six-sided columns of a gelatinous substance, in which 

 a number of nerve-fibres , originating in the spinal-marrow , 

 end in peculiar organs called nerve-end plates. The nervous 

 electricity is collected in this apparatus and discharged when 

 the fish is touched. The back is positive, the belly nega- 

 tive; and in order to receive a shock the visitor must touch 

 the fish on back and belly at once. The effect is considerably 

 weaker than in the South- American electric eel, but in a large 

 fully developed fish, is painful enough. After repeated dischar- 

 ges, the strength of the shock decreases. This organ is a wea- 



