THE ARGUMENTS FROM MORPHOLOGY. 409 



marked or they may be so fused as to make it difficult to find 

 the divisions between them, but they always exist. What 

 now can be the meaning of this community of structure 

 throughout the hundred thousand kinds of insects filling the 

 air, burrowing in the earth, swimming in the water? Why 

 under the down-covered body of a moth and under the hard 

 wing-cases of a beetle, should there be discovered the same 

 number of divisions? Why should there be no more somites 

 in the Stick-insect, or other Phasmid a foot long, than there 

 arc in a small creature like the louse? Why should the 

 inert Aphis and the swift-flying Emperor-butterfly bo con 

 structed on the same fundamental plan? It cannot be by 

 chance that there exist equal numbers of segments in all 

 these multitudes of species. There is no reason to think it 

 was necessary., in the sense that no other number would have 

 made a possible organism. And to say that it is the result 

 of design to say that the Creator followed this pattern 

 throughout, merely for the purpose of maintaining the pat 

 tern is to assign an absurd motive. No rational interpre 

 tation of these and countless like morphological facts, can be 

 given except by the hypothesis of evolution; and from the 

 hypothesis of evolution they are corollaries. If organic forms 

 have arisen from common stocks by perpetual divergences 

 and re-divergences if they have continued to inherit, more 

 or less clearly, the characters of ancestral races; then there 



the normal number of somites in the body of insects will be twenty, as in the 

 higher Crustacea and Araclinida&quot; To this passage, however, he puts the 

 note : &quot; It is open to question whether the podical plates represent a 

 somite; and therefore it must be recollected that the total number of 

 somites, the existence of which can be actually demonstrated in insects, is 

 only seventeen, viz., four for the head, three for the thorax, and ten for the 

 abdomen.&quot; I have changed the number twenty, which in the original 

 edition occurred in the text, to the number seventeen in deference to sug 

 gestions made to me ; though I find in Dr. Sharp s careful and elaborate 

 work on the Insecta, that Viallancs and Cholodkovsky agree with Huxley in 

 believing that there are six somites in the insect-head. The existence of a 

 doubt on this point, however, docs not essentially affect the argument, since 

 there is agreement among rnorphologists respecting the constancy of the total 

 number of somites in insects. 



