PANGENESIS 165 



of soil full of seeds, some of which soon germinate, some lie 

 dormant for a period, whilst others perish." : 



Darwin did not recognize the modern distinction between 

 somatogenic characters, which are acquired hy the body or soma 

 during its individual life-time, and blastogenic or germinal 

 characters, which are supposed to originate in the germ cells; or 

 rather, in accordance with his theory of pangenesis, he believed 

 that somatogenic modifications might be transferred to the germ 

 cells and thus become blastogenic. In other words, he was a 

 firm believer in the inheritance of acquired characters, a doctrine 

 which, as we shall see presently, is now much discredited, and 

 he endeavoured to explain by means of his theory how such 

 characters may be transmitted from parent to offspring. 



Suppose some part of the body in a particular multicellular 

 individual were to become modified by use or disuse, or by the 

 direct action of the environment. Then the gemmules given off 

 from the modified cells would also bo affected in a corresponding 

 manner and would carry information of the change to the germ 

 cells. It would be as if some constituency with many repre- 

 sentatives changed its political opinions and instead of sending 

 conservative members to the House of Commons took to sending 

 liberals. When the proper time came the new representatives 

 would vote according to their instructions ; but we must also 

 suppose that the old ones could never be turned out and that 

 there would be a struggle between the two. At first the old ones 

 would be the more numerous and would outvote the new ones; 

 presently, however, the new ones, being constantly reinforced, 

 would come to outnumber the old ones and perhaps be able to 

 give effect to the altered views of their constituency. As Darwin 

 says, " It is generally necessary that an organism should be 

 exposed during several generations to changed conditions or 

 habits, in order that any modification thus acquired should 

 appear in the offspring." It would probably be more in accord 

 with the facts if, instead of " several generations " we said 

 " a large number of generations." In this sense, we may 

 well believe that acquired characters can be inherited, without 

 expecting to be able to demonstrate such inheritance by cutting 

 off the tails of a few generations of mice. 



The theory of pangenesis certainly explains a great deal, but 

 it involves so many improvable assumptions as to the nature 



1 Loc. cit., pp. 398-9. 



