220 THE PHILOSOPHY OF BIOLOGY 



them, that is, may an acquired change of structure 

 be so fundamental that it affects not only the body 

 of the animal in which it occurs but also the progeny 

 of this animal ? Let us suppose that this is the 

 case ; let us suppose that quite a large proportion 

 of all the individuals of a species inhabiting a re- 

 stricted part of the earth's surface acquire the same 

 change of character simultaneously ; and that they 

 transmit this deviation of structure to their progeny. 

 Then we should have an adequate means whereby 

 the specific type becomes modified — a means of 

 transformism. 



This is the hypothesis which is associated with the 

 name of Lamarck, and its essential postulate is that 

 characters which are acquired by an organism during 

 its own lifetime are transmitted to its offspring. It 

 seems reasonable to suppose that this transmission 

 of acquired characters should occur — how reasonable 

 we should note when we see that de Vries tacitly 

 assumes that fluctuating variations due to the action 

 of the environment may be inherited by the offspring 

 of organisms which exhibit them. That transmutation 

 of species might occur in this way was a popular and 

 widespread belief in England and Germany through- 

 out the greater part of the nineteenth century ; and 

 it was a belief entertained by Darwin himself, and 

 confidently, and even dogmatically affirmed at one 

 time by the majority of biologists in both countries. 



How was it, then, that a very general change of 

 opinion with regard to this question occurred both in 

 England and Germany during the last two decades 

 of the last century ? Certainly many botanists and 

 zoologists continued to adhere to the older hypothesis, 

 and most physiologists still do not appear to make 

 any clear distinction between morphological characters 



