240 THE GENESIS OF SPECIES. [CHAP. 



says : l " Excessively minute and numerous as they are 

 believed to be, an infinite number derived, during a long 

 course of modification and descent, from each cell of each 

 progenitor, could not be supported and nourished by the 

 organism." 



But apart from these matters,, which, will be more fully 

 considered further on, the hypothesis not only does not 

 appear to account for certain phenomena which, in order 

 to be a valid theory, it ought to account for ; but it seems 

 absolutely to conflict with patent and notorious facts. 



How, for example, does it explain the peculiar reproduc- 

 tion which is found to take place in certain marine worms 

 certain annelids ? 



In such creatures we see that, from time to time, one of 

 the segments of the body gradually becomes modified till 

 it assumes the condition of a head, and this remarkable 

 phenomenon is repeated again and again, the body of the 

 worm thus multiplying serially into new individuals which 

 successively detach themselves from, the older portion. 

 The development of such a mode of reproduction by 

 " Natural Selection " seems not less inexplicable than does 

 its continued performance through the aid of " pangenesis." 

 For how can gemmules attach themselves to others to 

 which they do not normally or generally succeed \ 

 Scarcely less difficult to understand is the process of 

 the stomach- carrying-off mode of metamorphosis before 

 spoken of as existing in the Echinoderms. Next, as to 

 certain patent and notorious facts : On the hypothesis 

 of pangenesis, no creature can develop an organ unless it 

 possesses the component gemmules which serve for its 

 formation. No creature can possess such gemmules unless 



i "Animals and Plants under Domestication," vol. ii. p. 402. 



