ORGANIC EVOLUTION — THE FACTORS 123 



agents, but that the evolution of multicellular organisms 

 has resulted solely from the action of Natural Selection 

 — from the natural selection of inborn variations alone — 

 or, as Mr, Spencer holds, from the selection of inborn plus 

 acquired variations. 



If we hold, as I think we must, that the multicellular 

 organism is really a compound being, a being com- 

 pounded of unicellular organisms, then, as already ex- 

 plained, we must suppose that acc^uired variations are 

 not transmissible, unless it can be shown that tbe re- 

 productive cells receive from the somatic cells elements 

 Avhich so alter their constitutions as not only to cause 

 them to proliferate into organisms different from those 

 which would have otherwise arisen, but also into organ- 

 isms which have inborn in them variations which were 

 acquired in the cell-community of which the germ cells 

 were members. This is the next question discussed by 

 Mr. Spencer, but strangely enough he turns away from 

 the actual point at issue, the question as to whether the 

 elements (gemmules, physiological units, or what not) 

 which are supposed to cause the change in the constitu- 

 tion of the germ cell, have any real existence ; he assumes 

 that they do exist, and appears to think that all he 

 needs to prove is that, being existent, they are able to 

 enter the germ cells, and this he does by pointing out 

 that the microbes of disease as well as food molecules are 

 able to enter them. He proceeds — 



" Thus, then, the substance of the egg, and even its 

 innermost vital part, is permeable by a parasite suffici- 

 ently large to be microscopically visible. It is also, of 

 course, permeable by the invisible molecules of protein, 

 out of Avhich its living tissues are formed, and by the 

 absorption of which they subsequently grow. But, ac- 

 cording to Weismanu, it is not permeable by those in- 

 visible units of protoplasm out of which the vitally-active 



