



1588 CRUSTACEA. 



the hypothesis of migration by considering something beside the mere 

 possibility of its having taken place under certain assumed conditions. 

 The possibility of independent creations is as important a considera- 

 tion. After all the means of communication between distant pro- 

 vinces have been devised or suggested, the principle still comes up, 

 that it is in accordance with Divine Wisdom, to create similar and 

 identical species in different regions, where the physical circumstances 

 are alike ; and we must determine by special and thorough investi- 

 gation, whether one or the other cause was the actual origin of the 

 distribution in each particular case. Thus it must be with reference 

 to the wide distribution of species in the Oriental tropics, as well as in 

 the European temperate regions, and the Temperate zone of the South 

 Pacific and Indian Oceans. 



XII. With respect to the creation of identical species in distant 

 regions, we would again point to its direct dependence on a near iden- 

 tity of physical condition. Although we cannot admit that circum- 

 stances or physical forces have ever created a species (as like can 

 only beget like, and physical force must result simply in physical force), 

 and while we see in all nature the free act of the Divine Being, we 

 may still believe the connexion between the calling into existence of 

 a species and the physical circumstances surrounding it to be as inti- 

 mate nearly as cause and effect. The Creator has in infinite skill, 

 adapted each species to its place, and the whole into a system of ad- 

 mirable harmony and perfection. In his wisdom, any difference of 

 physical condition and kind of food at hand, is sufficient to require 

 some modification of the intimate structure of species, and this diffe- 

 rence is expressed in the form of the body or members, so as to pro- 

 duce an exactness of adaptation, which we are far from fully per- 

 ceiving or comprehending with our present knowledge of the relations 

 of species to their habitats. 



When therefore we find the same species in regions of unlike phy- 

 sical character, as, for example, in the seas of the Canaries and Great 

 Britain — regions physically so unlike — we have strong reason for 

 attributing the diffusion of the species to migration. The difference 

 between the Mediterranean and Great Britain may require the same 

 conclusion for the species common to these seas. They are so far 

 different, that we may doubt whether species created independently in 

 the two could have been identical, or even have had that resemblance 

 that exists between varieties ; for this resemblance is usually of the 



