610 



SCIENTIFIC THOUGHT. 



"Pan- 

 genesis." 



speculation of Darwin's which he put forward at the 

 end of his work on 'The Variation of Animals and 

 Plants under Domestication' (1868) the theory of 

 " Pangenesis." " This hypothesis implies that the whole 

 organisation, in the sense of every separate atom or unit, 

 reproduces itself. Hence ovules and pollen-grains, the 

 fertilised seed or egg as well as buds, include and consist 

 of a multitude of germs thrown off from each separate 

 atom of the organism." * These germs he calls gem- 

 mules, and admits that they agree to some extent with 

 Buffon's organic molecules, only that neither in these nor 

 in Spencer's physiological units does it seem clear that 

 each " independent or autonomous " organic unit, say 

 each cell, throws off or contributes its free gemmule (or 

 gemmules), which is capable of reproducing a similar 

 cell 2 



The theory of Pangenesis has not found much favour 

 with biologists. 3 For their purposes it would be neces- 



1 Loc. cit., vol. ii. p. 358. 



2 " Physiologists agree that the 

 whole organism consists of a multi- 

 tude of elemental parts, which are 

 to a great extent independent of 

 each other " (loc. cit., vol. ii. p. 

 368). Darwin then quotes Claude 

 Bernard (1866) and Virchow (1860) 

 on the doctrine of the " autonomy " 

 of cells : " I assume that the gem- 

 mules in their dormant state have 

 a mutual affinity for each other, 

 leading to their aggregation either 

 into buds or into the sexual ele- 

 ments" (p. 374). "Physiologists 

 maintain, as we have seen, that 

 each cell, though to a large extent 

 dependent on others, is likewise, to 

 a certain extent, independent or 

 autonomous. I go one small step 

 farther, and assume that each cell 



casts off a free gemmule, which is 

 capable of reproducing a similar 

 cell" (p. 377). "As each unit, or 

 group of similar units throughout 

 the body, casts off its gemmules, 

 and as all are contained within the 

 smallest egg or seed, and within 

 each spermatozoon or pollen- grain, 

 their number and minuteness 

 must be something inconceivable " 

 (p. 378). 



3 Grant Allen dismisses the 

 whole speculation in the fol- 

 lowing words : " The volume on 

 the variation of animals and 

 plants contained also Darwin's one 

 solitary contribution to the pure 

 speculative philosophy of life his 

 ' Provisional Hypothesis of Pan- 

 genesis, ' by which he strove to 

 account, on philosophical principles, 



