234 THE GENESIS OF SPECIES. [CHAP. 



this an important distinction, but it can hardly be so, for 

 Mr. Darwin considers that his gemmule has the innate 

 power and tendency to build up and transform itself into 

 the whole living, complex cell of which it forms a part ; and 

 the one tendency is, in principle, fully as difficult to under- 

 stand, fully as mysterious, as is the other. The difference 

 is but one of degree, not of kind. Moreover, the one mys- 

 tery in the case of the " physiological unit " explains all, 

 while with regard to the gemmule, as we have seen, it 

 has to be supplemented by other powers and tendencies, 

 each distinct, and each in itself inexplicable and profoundly 

 mysterious. 



That there should be physiological units possessed of 

 the power attributed to them, harmonizes with what has 

 recently been put forward by Dr. H. Charlton Bastian ; who 

 maintains that under fit conditions the simplest organisms 

 develop themselves into relatively large and complex ones. 

 This is not supposed by him to be due to any inheritance 

 of ancestral gemmules, but to direct growth and transforma- 

 tion of the most minute and the simplest organisms, which 

 themselves, by all reason and analogy, owe their existence 

 to immediate transformation from the inorganic world. 



Thus, then, there are grave difficulties in the way of the 

 reception of the hypothesis of Pangenesis, which, moreover, 

 if established, would leave the evolution of individual or- 

 ganisms, when thoroughly analyzed, little if at all less mys- 

 terious or really explicable than it is at present. 



As was said at the beginning of this chapter, " Pangen- 

 esis " and " Natural Selection " are quite separable and 

 distinct hypotheses. The fall of one of these by no means 

 necessarily includes that of the other. Nevertheless, Mr. 

 Darwin has associated them closely together, and, there- 

 fore, the refutation of Pangenesis may render it advisable 

 for those who have hitherto accepted " Natural Selection " 

 to reconsider that theory. 



