83 



in the beginning ; and, for the same reason (that is to 

 say, having no others of their kind to compare them 

 with), we cannot pronounce, even if we might assume 

 this partial organic decay to be the consequence of their 

 isolation on these rocks, whether their general stature 

 has been subsequently augmented or not. Still, there 

 are some few, out of the 200 just alluded to, which are 

 of common European distribution ; and, as these would 

 appear to have obeyed the principles to which we have 

 been calling attention, it is not unreasonable to suppose, 

 that many of the others (could we but behold them as 

 they formerly were, emigrants over a vast continuous 

 land) would be found to have done so also. 



I alluded, in a previous section, to the Dromius 

 obscuroguttatus, Dufts., as presenting permanent charac- 

 teristics in Madeira, the combined result of latitude 

 and isolation ; and I also stated that it was not always 

 possible, whilst dealing with physical agents which are 

 necessarily obscure, to refer the respective phenomena 

 (whatsoever they may be), which would seem to have 

 departed from their types, to a single disturbing cause. 

 Hence, whilst I there acknowledged latitude as in part 

 answerable for the changes which that insect has under- 

 gone, I may here suggest that it is, in all probability, 

 to isolation that we must mainly look, if we would under- 

 stand those changes aright. But what are the distinctive 



will not tend to diminish the probability that there is something 

 peculiar in the action of Madeiran influences generally on the alary 

 system of the insect tribes. 



