100 EVOLUTION AND MAN S PLACE IN NATURE 



so astonishing as to baffle conception. To suppose 

 that inheritance of the characteristics of the species, 

 and of variations acquired by immediate progenitors, 

 is secured by planting a representative gem mule within 

 the germ-cell, is to make too large a demand on 

 imagination. There seems little doubt that Darwin s 

 hypothesis as to pangenesis must be abandoned. 



When next we turn to Weismann s hypothesis, 

 there are many serious difficulties in the way of its 

 acceptance. The chief of these come from the field 

 of observation occupied by the naturalist. When 

 Darwin s hypothesis is compared with that of Weis- 

 mann, each is strong in the field with which its 

 author is most familiar; each is weak on the side 

 towards which his research has been least directed. 

 But Weismann has this great advantage, that his 

 chosen field of observation places him in relation 

 with the problems of cell-life. His hypothesis is 

 favoured in its start by the fact that the germ-cells 

 are severed from the somatic cells, being set apart 

 for the function of reproduction. While pangenesis 

 suffers by diffusion of the work over the body, 

 Weismann s theory gains by concentrating on these 

 cells. Too much, however, seems to be made of 

 isolation of the germ-cells, which certainly are not 

 severed from the vascular and nerve systems. Allow 

 ance, therefore, must be made for possible modifica 

 tions in their structure in this way. The changes 

 within the nucleus, the sending out of so-called polar 

 bodies, the splitting of the nuclear fibres, and all 

 the other characteristics of cellular movements, favour 

 the hypothesis that the germ-cell contains within 

 itself, however dependent on the parent body, the 



