History of the Theory of Heredity. 51 



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in their dormant state hare a mutual affinity for each 

 other, leading to their aggregation either into buds or 

 into the sexual elements. Hence, speaking strictly, it is 

 not the reproductive elements nor the buds which gene- 

 rate new organisms, but the cells themselves throughout 

 the body. These assumptions constitute the provisional 

 hypothesis of pangenesis.'*' 



Darwin's gemmules are, of course, entirely imaginary, 

 that is, a belief in their existence does not rest upon 

 direct observation. "We cannot deny that the hypothesis 

 furnishes an explanation of most of the phenomena 

 which he attempts to interpret by it, although it seems 

 possible that there may be a simpler ex[)lanation. If the 

 existence of the gemmules were proven we could under- 

 stand not only the wonderful facts of ordinary inheri- 

 tance by sexual reproduction, but the various forms of 

 asexual reproduction as well. 



We should have a simple explanation of the manner 

 in which the characteristics of a remote ancestor may 

 suddenly reappear after they have been dormant for 

 many Sfenerations. We should understand how the em- 

 bryological history of a species may become simplified 

 by the omission of larval forms or appendages. In a 

 word, nearly all the phenomena of heredity admit of 

 explanation by the hypothesis, and those wdio have criti- 

 cised it have not usually attempted to show that it con- 

 flicts with fact, but have simply objected to it as a purely 

 imaginary explanation. It is urged that the transmis- 

 sion of all the characteristics which we know to be in- 

 herited from near and remote ancestors demands that 

 the number of gemmules should be almost unlimited and 

 practically infinite; that not only are the gemmules im- 

 aginary, but that the aggregation of such numbers in 

 masses as small as the reproductive elements requires 



