EVOLUTION OF THE COLORS OF BIRDS. 57 



are we to conceive of these ancestral units, the ahnen- 

 plasmas? Two hypotheses may be given in answer to 

 this question: 



A. Each ahneiiplasma unit corresponds to an in- 

 dividual of the species itself; and if put under proper 

 tropic conditions, would, singly, reproduce such an in- 

 dividual. 



B. The ahnenplasmas correspond to the primitive 

 Protozoan ancestors, which, according to theory, could 

 alone reproduce modifications due to external causes 

 (acquired modifications)." 



Prof. Hartog then shows that if hypothesis A be ac- 

 cepted the ahnenplasmas must have varied with the 

 race, but this would make the shufiiing process super- 

 fluous as an explanation ol variation, and would also be 

 contradictory to thesis II. 



"According to hypothesis B/' he continues, " the 

 ahnenplasmas of all Metazoa being similar and Proto- 

 zoan, if the numbers are equal and the shuffling fair, any 

 two parents may beget any offspring whatever; on the 

 plane of thesis V, a lioness might be expected to bring 

 forth a lobster or a starfish or any other animal, which 

 as we know, does 1101 take place in nature. The only 

 escape from this result is to assume the postulates (1) 

 that the number of ahnenplasmas varies from species to 

 species; (2) that the number in the combination and 

 not the character of the ahnenplasmas determines the 

 species. And as there is not a particle of evidence for 

 the latter postulate, we may say that on hypothesis B. 

 the theory breaks down by its non-conformity with the 

 facts. 



We have then the dilemma, from which I see no 

 escape, that the theory is inconsistent, on A with itself, 

 on B with the facts." 



It is too soon to attempt to pass judgment upon this 



