OTHER FACTORS OF EVOLUTION 121 



direct influence of conditions, one might have thought that the last 

 persons to start such an objection would be Weismann and his 

 followers, looking to the extraordinarily complex mixture of assump- 

 tions and hypotheses by which their own attempted explanation of 

 heredity is sought to be supported. 



Some of Herbert Spencer's last words on this subject may well 

 be quoted here. In his " Facts and Comments " (1902, p. 92) he 

 says: — "The doctrine of use-inheritance is rejected because of 

 inability to ' conceive any means ' by which a modification produced 

 in an organ, can produce a correlated modification in the germ of 

 a descendant. Yet the alternative hypothesis is accepted notwith- 

 standing a kindred inability which is certainly not less and may be 

 held much greater. If Weismann's view is true, such a structure 

 as a peacock's tail feather implies over 300,000 determinants. 

 Multiply that by the number of such feathers, and add those of the 

 body feathers, as well as those of all the parts of all the organs, 

 and then imagine the number of determinants which must be 

 contained in the microscopic sperm-cell. Further imagine that in 

 the course of the developmental transformations, each determinant 

 finds its way to the place where it is wanted ! Surely to ' conceive 

 any means' by which these requirements may be fulfilled, is 

 not a smaller difficulty if it is not a greater," than that which has 

 to be met in connection with the doctrine of 'physiological 

 units.' ' 



The question of relative conceivability between Weismann's 

 doctrine of absolutely innumerable determinants in the germ- 

 plasm, destined to produce corresponding parts in the offspring, 

 and Spencer's doctrine of physiological units cannot by any possi- 

 bility be said to be easier for the former doctrine ; and when one 

 considers how this doctrine utterly fails to explain multitudes of 

 known facts concerning repair and regeneration in animals, and 

 reproduction by buds, cuttings and superficial cells in plants, with 

 which Spencer's doctrine is quite in harmony, there ought not to 

 be room for doubt as to which hypothesis is most in accord with 

 facts. And in reference to the conceivability of this latter doctrine, 



' The above is an under statement of the case as to the conceivability of 

 Weismann's views, because the " sperm-cell " contains a number of chromo- 

 somes, and each of these bodies is made up of a number of granules— the ids— 

 and each one of these granules is supposed to contain the total number of 

 determinants referred to above, for the building-up of the body, which Spencer 

 speaks of as contained in the entire " sperm-cell." 



