INHERITANCE OF ACQUIRED CHARACTERS 177 



or give rise to, a blastogenic one? In other words Can a 

 modification of the body or soma, arising in the life- time of the 

 individual and itself in no way due to inheritance, affect the 

 germ cells in such a way that the offspring developed from 

 them will exhibit a corresponding modification of its soma ? 



It is useless either to deny or to assert the possibility of the 

 inheritance of such characters on any purely a priori grounds. 

 The fact that no satisfactory mechanism for the transference of 

 such characters from parent to offspring has yet been demon- 

 strated does not justify us in denying the possibility of such 

 transference. Our decision must depend upon an unbiassed 

 examination of the evidence which can be brought forward on 

 each side. 



It is, of course, obvious that inasmuch as any organism differs 

 to a greater or less extent from its ancestors, the differences 

 being as a general rule greater in proportion to the remoteness 

 of the particular ancestor with which it is compared, the 

 differentiating characters must have been acquired, in the 

 ordinary sense of the word, during the interval which separates 

 the two generations in question. For example, there can be no 

 reasonable doubt that birds are descended from ancestors which 

 were reptilian in character and had no feathers. Feathers have 

 unquestionably been acquired somehow or other during the pro- 

 gress of the bird's evolution. This, however, is not the sort of 

 acquisition the inheritance of which is in dispute. Weismann and 

 his followers would deny altogether that feathers originated as 

 somatogenic characters ; they would say that certain apparently 

 fortuitous modifications in the constitution of the germ cells 

 themselves were responsible for the first appearance of feathers 

 probably in an extremely rudimentary form and that this new 

 character proving to be of value in the struggle for existence was 

 preserved and fostered by natural selection until after a long 

 process of evolution the elaborate plumage of existing birds was 

 perfected. 



In striking contrast to such a case as the above we have 

 innumerable cases of the more or less sudden appearance of 

 somatic characters during the life-time of an individual as the 

 obvious result of the action of some external or environmental 

 influence, or of the use or disuse of some organ by its possessor, 

 and it is to such cases that Weismann and his followers would, 

 rightly or wrongly, confine the discussion. 



B. N 



