KELATION OF SPECIES TO GENUS. 429 



causes. During his growth he undergoes numerous meta- 

 morphoses, too numerous even for the human imagination. 

 These have a relation to the organic world. They embrace 

 the entire range of organic life, from the beginning to the 

 end of time. Nature can have no double systems ; no amend- 

 ments or second thoughts ; no exceptional laws. Eternal and 

 unchanging, the orbs move in their spheres precisely as they 

 did millions of years ago. Proceeding, as it were, from an 

 invisible point endowed with life, he passes rapidly, at first, 

 through many forms, all resembling, more or less, either dif- 

 ferent races of men from his own, or animals lower in the scale 

 of being ; or beings which do not now exist, though the} 7 pro- 

 bably once did, or may at some future time. When his develop- 

 ment is imperfect, it represents then some form, resembling the 

 inferior races of men, or animals still lower in the scale of being. 

 Moreover, what is irregular in him is the regular structure in 

 some other class of animals. Take for example the webbed 

 hand or foot occasionally found in man, constant in certain 

 animals as in the otter and beaver ; constant also in the 

 human foetus, that is, the child before birth. Take, for ex- 

 ample, the cuticular fold at the inner angle of the eye, so 

 common with the Esquimaux and Bosjesman or Hottentot 

 (the corresponding yellow races of the northern and southern 

 hemispheres), so rare in the European, but existing in every 

 foetus of every race. Nor let it be forgotten that forms exist 

 in the human foetus which have nothing human in them in 

 the strictest sense of the term ; that the foetus of the Negro 

 does not, as has been stated, resemble the foetus of the Euro- 

 pean, but that the latter resembles the former, all the more 

 resembling the nearer they are to the embryonic condition. 

 Unity of structure, unity of organization, unity of life, at the 

 commencement of time, whether measured by the organic world 

 or by the duration of individual life." This is the law. 



The relation of species to genus also merits our deepest 

 attention.* 



" My first observations were made on animals low in the 

 scale of the vertebrata on fishes, in fact. I selected, as 1 

 shall presently more fully explain, the natural family of the 

 Saltnonidse, as the one to which I had given most attention. 

 In the young of the true salmon I found the specific charac- 

 ters of all the sub-families of the genus present ; that is, red 

 spots, dark spots of several kinds, silvery scales, proportions, 



* See " Memoirs on the Philosophy of Zoology," in The Zoologist. J. Vau 

 Voorst, London. 



