FACTORS OF ORGANIC EVOLUTION 



ly stated, this resolves itself into the assertion that 

 the progeny of such bacteria, often after tens or 

 hundreds of generations, are possessed of a char- 

 acter which was acquired by their ancestors during 

 their passage through the body of the susceptible 

 animal. This is as clear a case of the transmission 

 of acquired characters as any one can ask for. 

 It does not follow from this that all acquired 

 character, in one of the higher animals or plants, 

 can be transmitted; but it is something to have 

 an instance, familiar and indisputable, which 

 cannot be reconciled with the dogma of Weis- 

 mann. 



Certain acquired characters cannot be con- 

 ceived to affect the germ-cells of an individual of 

 one of the higher types. These cells are certainly 

 not, as Darwin supposed, formed by pangenesis 

 that is to say, by contribution of representative 

 units from all the cells of the body. On the con- 

 trary, we are now compelled to believe, with Weis- 

 mann, in the doctrine of the "continuity of the 

 germ-plasm," which asserts that the original cell 

 from which any individual is formed divides into 

 two portions, one of which becomes the individual 

 and the other his own germ-cells. If this be true, 

 acquired characters can be transmitted only when 

 they can influence the germ-cells through the blood- 

 stream. Certain characters, such as immunity to 

 disease, may conceivably be thus transmitted, but 

 there is no room for belief in the transmission 

 of such an acquired character as baldness, any 

 I2 S 



