4 ;6 THE POPULAR SCIENCE MONTHLY. 



something which it is " easy to imagine," but he assumes some- 

 thing which it is difficult to imagine ; and apparently thinks that 

 a scientific conclusion may be thereupon safely based. 



But now to what end are we asked to make a gratuitous " sup- 

 position," to accept as true something strange which is "quite 

 conceivable," and to strain our imaginations without the slight- 

 est aid from the evidence ? Simply to save Prof. Weismann's 

 hypothesis to shelter it against a great body of adverse facts. 

 When we have recognized the truth that what he regards as a 

 primary division of labor is no division of labor at all when we 

 see that the corollary he draws respecting the implied primary 

 differentiation of reproductive cells from somatic cells is conse- 

 quently without warrant ; we have no occasion to feel troubled 

 that his deductive conclusion is inductively disproved. We are 

 not dismayed on finding that throughout vast groups of organ- 

 isms there is shown no such antithesis as his theory requires. 

 And we need not do violence to our thoughts in explaining away 

 the contradictions. 



Associated with the assertion that the primary division of 

 labor is between the somatic cells and the reproductive cells, and 

 associated with the corollary that the primary differentiation is 

 that which arises between them, there goes another corollary. It 

 is alleged that there exists a fundamental distinction of nature 

 between these two classes of cells. They are described as respect- 

 ively mortal and immortal, in the sense that those of the one class 

 are limited in their powers of multiplication, while those of the 

 other class are unlimited. And it is contended that this is due to 

 inherent unlikeness of nature. 



Before inquiring into the truth of this proposition, I may fitly 

 remark upon a preliminary proposition set down by Prof. Weis- 

 mann. Referring to the hypothesis that death depends "upon 

 causes which lie in the nature of life itself," he says : 



*'I do not however believe in the validity of this explanation; I consider that 

 death is not a primary necessity, hut that it has been secondarily acquired as an 

 adaptation. I believe that life is endowed with a fixed duration, not because it 

 is contrary to its nature to be unlimited, but because the unlimited existence of 

 individuals would be a luxury without any corresponding advantage " (p. 24). 



This last sentence has a teleological sound which would be 

 appropriate did it come from a theologian, but which seems 

 strange as coming from a man of science. Assuming, however, 

 that the implication was not intended, I go on to remark that 

 Prof. Weismann has apparently overlooked a universal law of 

 evolution not organic only, but inorganic and super organic 

 which implies the necessity of death. The changes of every aggre- 





