The Zoologist — September, 1868. 1357 



have passed away, are numerically insignificant when compared with 

 the multitude of insect races that are gradually disappearing from the 

 surface of the earth. Every writer on geographical Zoology con- 

 tributes his quota of information on this deeply interesting subject, 

 although in no instance, so far as my reading has extended, has the 

 knowledge of this fact been rendered available for advancing a com- 

 prehensive theory. I will quote only one : Mr. Wollaston, after 

 speaking of a group of insects which infest the Euphorbias of the 

 Atlantic Archipelago, and describing them as " without a parallel, 

 both as regards the number of the individuals by which they are 

 severally represented and the greater or less eccentricity of their 

 structure," goes on to assert that " the quaint and grotesque shrubs on 

 which this esoteric assemblage depends for subsistence, are becoming 

 gradually exterminated. 1 ' He continues : " True it is that the process 

 of annihilation is extremely slow; yet, year after year sees portions of 

 the rocky declivities brought into rude cultivation, whilst the constant 

 search which is made after the dead plants for fuel still further 

 operates to direct the axe of the destroyer. Here then we have an 

 unmistakable fact, and one over which it is worth while to pause — not 

 of a single species, but of a tvhole fauna surely dying out before 

 circumstances which were adverse to its continuance. * * * In 

 two of the islands, Lanzarote and Fuertevenlura, Euphorbia canariensis 

 seems to have already gone ; and what is the consequence ? Simply 

 that not one of the numerous species which characterize that plant 

 appears to have adapted itself even to the other Euphorbians. And if 

 this be the case, can we wonder that the extinction of the latter should 

 result in the complete disappearance and for ever of their entire 

 fauna ? " Probably in reference to the hypothesis of evolution hereafter 

 briefly noticed, Mr. Wollaston remarks, " In vain do we look around 

 for anything like an adaptation to altered, and ever altering, condi- 

 tions ; and I will venture to aflirm that no one instance can be 

 produced throughout this noble fauna, in which the slightest ten- 

 dency is shown by even a single species to accommodate itself to 

 the change of circumstances, and to become modified accordingly." 

 It may here be observed that the laurel fauna of the same inte- 

 resting islands is as clearly on its way to extinction as that of the 

 Euphorbia?. 



Thus we see that the number of species in the world of animals 

 is decreasing year by year, month by month, and probably day by 

 day. 



