108 THE GENESIS OF SPECIES. [CHAP. 



Many cases have been adduced of striking likenesses 

 between different animals, not due to inheritance ; but this 

 should be the less surprising, in that the very same indi- 

 vidual presents us with likenesses between different parts 

 of its body (e. g., between the several joints of the back- 

 bone), which are certainly not so explicable. This, how- 

 ever, leads to a rather large subject, which will be spoken 

 of in the eighth chapter of the present work. Here it will 

 be enough to affirm (leaving the proof of the assertion till 

 later) that parts are often homologous which have no di- 

 rect genetic relationship a fact which harmonizes well 

 with the other facts here given, but which " Natural Se- 

 lection," pure and simple, seems unable to explain. 



But surely the independent appearance of similar or- 

 ganic forms is what we might expect, a priori, from the 

 independent appearance of similar inorganic ones. As Mr. 

 G. H. Lewes well observes : * 6 f< We do not suppose the car- 

 bonates and phosphates found in various parts of the globe 

 we do not suppose that the families of alkaloids and 

 salts have any nearer kinship than that which consists in 

 the similarity of their elements, and the conditions of their 

 combination. Hence, in organisms, as in salts, morpho- 

 logical identity may be due to a community of casual con- 

 nection, rather than community of descent. 



" Mr. Darwin justly holds it to be incredible that indi- 

 viduals identically the same should have been produced 

 through Natural Selection from parents specifically dis- 

 tinct, but he will not deny that identical forms may issue 

 from parents genetically distinct, when these parent forms 

 and the conditions "of production are identical. To deny 

 this would be to deny the law of causation." 



Prof. Huxley has, however, suggested 27 that such min- 

 eral identity may be explained by applying also to minerals 



26 Fortnightly Review, New Series, vol. iii. (April, 1868), p. 372. 

 87 " Lay Sermons," p. 339. 



