DIFFICULTIES OF THE THEORY 261 



distribution of the nerves, and in the manner in which 

 they are acted on by various reagents. It should, also, be 

 especially observed that muscular contraction is accom- 

 13anied by an electrical discharge; and, as Dr. Eadcliffe 

 insists, "in the electrical apparatus of the torpedo during 

 rest there would seem to be a charge in every respect 

 like that which is met with in muscle and nerve during 

 rest, and the discharge of the torpedo, instead of being 

 peculiar, may be only another form of the discharge which 

 attends upon the action of muscle and motor nerve." 

 Beyond this we cannot at present go in the way of 

 explanation; but as we know so little about the uses 

 of these organs, and as we know nothing about the habits 

 and structure of the jDrogenitors of the existing electric 

 fishes, it would be extremely bold to maintain that no 

 serviceable transitions are possible by which these organs 

 might have been gradually developed. 



These organs appear at first to offer another and far 

 more serious difficulty; for they occur in about a dozen 

 kinds of fish, of which several are widelv remote in their 

 affinities. "When the same organ is found in several mem- 

 bers of the same class, especially if in members having 

 very different habits of life, we may generally attribute 

 f I its presence to inheritance from a common ancestor; and 

 )r I its absence in some of the members to loss through disuse 

 or natural selection. So that, if the electric organs had 

 been inherited from some one ancient progenitor, we 

 might have expected that all electric fishes would have 

 been specially related to each other; but this is far from 

 the case. Nor does geology at all lead to the belief that 

 most fishes formerly possessed electric organs, which their 

 modified descendants have now lost. But when we look 



