O^ohgical Society. 443 



that ail kinds of excitants act in tlie same way, the effects differing 

 in intensity, not in direction. In all these respects, and in others 

 of less importance, the electrical plate agrees with muscle and 

 nerve. Inasmuch, therefore, as we have met with a structure of 

 which the development of electrical action is the exclusive function, 

 there seems to be good reason for the hope that by its investigation 

 a nearer approach may be made than has hitherto been possible to 

 the central question — that of the reason why in all animal struc- 

 tures the transition from the inactive to the active state is, so far as 

 our present knowledge teaches, always accompanied by electrical 

 change. 



The question why certain fish are endowed with so singular a 

 means of offence and defence, which others allied to them zoologi- 

 cally do not possess, and, above all, why some fish have electrical 

 organs so small as to be useless, is as difficult to answer now as 

 when Mr. Darwin wrote the ' Origin of Species.' The facts relating 

 to the development of the organ, which teach us to regard it as, in 

 some sense, a modified muscle, might suggest that the transition 

 from muscle to organ was a gradual one, determined by external 

 conditions. But we are prevented from accepting any such sugges- 

 tion by the consideration that an electrical organ only becomes 

 advantageous to its possessor when it has acquired sufficient size to 

 be used in the capture of prey, and that in all previous stages of 

 transition it must be useless. Natural selection could not therefore 

 determine the development of the electrical organ by modification 

 of muscle. It is more reasonable to imagine that all fish, or at any 

 rate certain families of fish, possess an undeveloped element of 

 structure, of which the electrical organ is the manifestation. So 

 that what we have to account for is not its presence in some excep- 

 tional cases, but its absence in the great majority. 



The existence of such a tendency as this hypothesis supposes 

 would render it possible for natural selection to operate efficiently 

 in bringing about the observed result. 



GEOLOGICAL SOCIETY. 



November 9, 1887.— Prof. J. W. Judd, F.R.S., 

 President, in the Chair. 



The following communication was read : — 



" Note on the so-called ' Soapstone ' of Fiji." By Henry B. 

 Brady, F.R.S. 



The Suva deposit, which has a composition very similar to that 

 of the volcanic muds at present forming around oceanic islands in 

 the Pacific, is friable and easily disintegrated. The colour ranges 

 from nearly white to dark grey, the mass being usually speckled 



31* 



