Heredity and the O right of Variations. 133 



gemmules remained latent to develop in the second or 

 third generation. The regeneration of lost parts receives 

 also a ready explanation. If a part be removed by ampu- 

 tation, regrowth is possible because there are disseminated 

 throughout the body gemmules derived from each part and 

 from every organ. A stock of nascent cells or of partially 

 developed gemmules may even be retained for this special 

 purpose, either locally or throughout the body, ready to 

 combine with the gemmules derived from the cells which 

 come next in due succession. Similarly, in budding, the 

 buds may contain nascent cells or gemmules in a some- 

 what advanced stage of development, thus obviating the 

 necessity of going through all the early stages in the 

 genesis of tissues. The gemmules derived from each part 

 being, moreover, thoroughly dispersed through the system, 

 a little fragment of such an organism as hydra may con- 

 tain sufficient to rebuild the complete organism ; or, if it 

 contains an insufficient number, we may assume that the 

 gemmules, in their undeveloped state, are capable of multi- 

 plying indefinitely by self-division. Finally, variations 

 might arise from the superabundance of certain gemmules 

 and the deficiency of others, and from the varying potency 

 of the gemmules contained in the sperm and ovum. Where 

 the maternal and paternal gemmules are of equal potency, 

 the cell resulting from their union will be a true mean 

 between them ; where one or other is prepotent, the result- 

 ing cell will tend in a corresponding direction. And since 

 the parental cells are subject to modification, transmitted 

 through the gemmules to the reproductive elements, it is 

 clear that there is abundant room and opportunity for 

 varietal combinations. 



It is claimed, as one of the chief advantages of some 

 form of pangenetic hypothesis, that it, and it alone, enables 

 us to explain the inheritance of characters or modifications 

 of structure acquired by use (or lost by disuse) during the 

 life of the organism, or imprinted on the tissues by en- 

 vironmental stresses. The evidence for the transmission 

 of such acquired characters we shall have to consider 



