THE THEORY OF PANGENESIS 



4i 



An attempt to solve the difficulty which confronted the 

 preformationists — the difficulty of accounting for the complex 

 organisation presumed to exist in the germ-cell — is expressed 

 in a theory which seems to have occurred at intervals in the long 

 period between Democritus and Darwin, the theory of pangenesis. 

 On this theory the cells of the body are supposed to give off 

 characteristic and representative gemmules ; these are supposed 

 to find their way to the reproductive elements, which thus come 

 to contain, as it were, concentrated samples of the different 

 components of the body, and are therefore able to develop into 



Fig. 8. — Forms of spermatozoa, enormously magnified, not drawn to 



scale. 



1 and 2, Immature and mature spermatozoa of snail ; 3, of bird ; 4, of man — h. head, m, 

 middle portion, t, tail ; 5, of salamander, with vibratile fringe (/) ; 6. of Ascaris, slightly 

 amoeboid, with cap (c) ; 7, of crayfish. 



an offspring like the parent. The theory is avowedly unverifiable 

 in direct sense-experience, but the same may be said of many 

 other hypotheses, and is not in itself a serious objection. It is 

 more to the point to notice that it involves many hypotheses, 

 some of them difficult to accept even provisionally. Galton long 

 ago tried, by experiments on the transfusion of blood, to test one 

 of these hypotheses, and found no confirmation. But it is 

 still more to the point to notice that there is another theory of 



