52 INTRODUCTION. 



muscles ; and the contraction, by the action of the 

 abdominal muscles. This mode of respiration is 

 not unknown in some of the molluscous animals, 

 whose branchial membrane exactly resembles that 

 yust described. Were the animal examined during 

 life, it would undoubtedly exhibit numerous cilia, 

 not only for renewing the supply of water for re- 

 spiration, but also for conveying food to the orifice 

 of the digestive organ. This orifice is guarded by 

 filaments, acting as a sieve to prevent the entrance 

 of foreign bodies, or of such food as it has neither 

 jaws to masticate, nor powers of stomach to 

 digest. 



In conclusion, it is to be observed that no 

 opportunity has occurred for examining this fish 

 when alive, so that much remains to be done in the 

 investigation of its peculiar habits : and, moreover, 

 that the peculiarities of the hepatic, renal, and 

 other systems of this most anomalous of vertebrate 

 animals, still leaves much for the examination of 

 the physiologist. 



THE ELECTRIC ORGAN OF THE SILURUS 

 OP THE NILE. 



The exact structure of the Electric Organ of the 

 Silurus of the Nile, Malapterurus electricus, being 

 now ascertained, we shall avail ourselves of the 

 researches regarding this apparatus by M. Valen- 

 ciennes, as contained in the last volume of his great 

 work on Fishes which has reached this country. 



