Mr. T. V. Wollaston on the Tarphii. 377 



graphically or structurally, we may feel virtually certain that the 

 two nuclei, although cast (so to speak) in the same mould, were ab- 

 originally distinct. Taking this therefore for granted (which I am 

 satisfied that all candid observer's who are acquainted practically 

 with these creatures and their life-histories would do), I leave it 

 to the advocates of the new hypothesis to decide how it is that in, 

 at any rate, two remote parts of the world (Sicily and the sub- 

 African islands of the northern Atlantic) independent organisms 

 should have been slowly and systematically modifying themselves, 

 through countless ages and under totally different circumstances, in 

 so precisely the same undeviating direction that they have arrived 

 ultimately at structures, complex and most peculiar, which are so 

 nearly the same that they must now be treated as generically iden- 

 tical. If this can be conceived possible through the operation of any 

 mere " selecting power of nature," guided by chance agencies from 

 without, it will be useless in future to bring forward any facts to 

 confront the theory at all ; and we must leave it to be " demon- 

 strated" by the less tedious and more poetical method of pure imagi- 

 nation. 



Having been induced to touch upon this question of specific dis- 

 tribution, as instanced by Tarphius and its outlying Sicilian member, 

 I have taken the opportunity of dwelling upon it thus at length, not 

 on account of any peculiarity in the example selected (which is but 

 one out of hundreds of a similar kind, as every practical naturalist 

 is aware), but simply for the sake of recording the partimlar con- 

 siderations bearing upon a certain newly-revived (but by no means 

 modern) doctrine, which one of the commonest classes of facts in 

 geographical zoology has always seemed to me to be capable of 

 directly engendering. And although I have purposely confined my 

 remarks to members of the same actual genus — for I have desired to 

 limit the problem to creatures which everybody will spontaneously 

 acknowledge to be what, through the poverty of language, we con- 

 ventially term " nearly allied," — I would nevertheless beg the reader 

 to observe that they are equally applicable to all organisms which 

 possess (inter se) great structural resemblance, whether or not they 

 be so similarly constituted as to require a positive admission into 

 what we call (often without much real precision, and very gratui- 

 tously) the same " genus." So that if the above suggestions should 

 carry with them any weight when applied to the absolute Tarphii of 

 the Atlantic islands as compared with the representative from Sicily, 

 the enormous interval between both of those regions and Southern 

 India will a fortiori impart to the pseudo- Tarphii of the latter a 



