188 FISHES. 



sensitive, and perish even from the superficial abrasion caused 

 by the meshes of the net during capture {Mullsn.) 



The power of repi^oduction of lost paiis in Teleosteous 

 fishes is limited to the delicate terminations of their fin-rays 

 and the various tegumentary filaments with which some are 

 provided. These filaments are sometimes developed in an 

 extraordinary degree, mimicking the waving fronds of the sea- 

 weed in which the fish hides. Both the ends of the fin-rays 



Fig_ 97. — Pike caught in the Thames, which, when young, had lost part of the 

 tail with the caudal fin. 



and the filaments are frequently lost, not only by accident, but 

 merely by wear and tear ; and as these organs are essential 

 for the preservation of the fish, their reproduction is necessary. 

 In Dipnoi, Ceratodiis, and Protopterus, the terminal portion 

 of the tail has been found to have been reproduced, but with- 

 out the notochord. 



Hybernation has been observed in many Cyprinoids and 

 Mursenoids of the temperate zones. They do not fall into a 

 condition of complete torpidity, as Reptiles and Mammals, 

 but their vital functions are simply lowered, and they hide 

 in sheltered holes, and cease to go abroad in search of their 

 food. Between the tropics a great number of fishes (especi- 

 ally Siluroids, Labyrinthici, Ophiocephaloids, the Dipnoi), 

 are known to survive long-continued droughts by passing 

 the dry season in a perfectly torpid state, imbedded in the 

 hardened mud. Protopterus, and probably many of the other 

 fishes mentioned, prepare for themselves a cavity large enough 

 to hold them, and coated on the inside with a layer of 

 hardened mucus, which preserves them from complete desic- 



