106 THE GENESIS OF SPECIES. [CHAP. 



Here it will be enough to affirm (leaving the proof of the 

 assertion till later) that parts are often homologous which 

 have no direct genetic relationship a fact which harmonizes 

 well with the other facts here given, but which " Natural 

 Selection/' pure and simple, seems unable to explain. 



But surely the independent appearance of similar organic 

 forms is what we might expect, a priori, from the indepen- 

 dent appearance of similar inorganic ones. As Mr. G. H. 

 Lewes well observes: 1 "We do not suppose the carbonates 

 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, morpholo- 

 gical identity may be due to a community of causal con- 

 nexion, 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 distinct; 

 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." 



Professor Huxley has, however, suggested 2 that such 

 mineral identity may be explained by applying also to 

 minerals a law of descent ; that is, by considering such 

 similar forms as the descendants of atoms which inhabited 

 one special part of the primitive nebular cosmos, each con- 

 siderable space of which, may be supposed to have been 

 under the influence of somewhat different conditions. 



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

 2 "Lay Sermons," p. 339. 



