224: THE GENESIS OF SPECIES. [CHAP. 



each ovum and spermatozoon in most animals, and each part 

 capable of reproducing by gemmation (budding) in the low- 

 est animals and in plants. Therefore in many of such low- 

 er organisms such a congeries of ancestral gemmules must 

 exist in every part of their bodies, since in them every part 

 is capable of reproducing by gemmation. Mr. Darwin 

 must evidently admit this, since he says : " It has often 

 been said by naturalists that each cell of a plant has the 

 actual or potential capacity of reproducing the whole 

 plant ; but it has this power only in virtue of containing 

 gemmules derived from every part" l 



Moreover, these gemmules are supposed to tend to 

 aggregate themselves, and to reproduce in certain definite 

 relations to other gemmules. Thus, when the foot of an 

 eft is cut off, its reproduction is explained by Mr. Darwin 

 as resulting from the aggregation of those floating gem- 

 mules which come next in order to those of the cut surface, 

 and the successive aggregations of the other kinds of gem- 

 mules which come after in regular order. Also, the most 

 ordinary processes of repair are similarly accounted for, 

 and the successive development of similar parts and organs 

 in creatures in which such complex evolutions occur is ex- 

 plained in the same way, by the independent action of 

 separate gemmules. 



In order that each living creature may be thus furnished, 

 the number of such gemmules in each must be inconceiv- 

 ably great. Mr. Darwin says : 3 "In a highly-organized 

 and complex animal, the gemmules thrown off from each 

 different cell or unit throughout the body must be incon- 

 ceivably numerous and minute. Each unit of each part, as 

 it changes during development and we know that some 

 insects undergo at least twenty metamorphoses must 

 throw off its gemmules. All organic beings, moreover, 



1 " Animals and Plants under Domestication," vol. ii., p. 403. 

 8 Ibid., p. 366. 



