7O THOUGHTS ON NATURAL PHILOSOPHY. 



*heredity, and the differences of the power of the 

 skin, etc., is that which allows of such great varia- 

 tion. But it is not only the power of the skin, there 

 is also the question of the tsize of the cells. The 

 cells of some things are larger than the cells of 

 others, and contain a larger quantity, if not a better 

 quality, of nutrient matter; and consequently the 

 daughter cells are larger, and as they increase and 

 grow you get a larger object. There is more, how- 

 ever, than the mere question of size, there is likeness. 

 Why an elephant and not a fish ? The reply is that 

 it is a question of the most delicate play of complex 

 physical forces. Every reproductive cell, if it could 

 be seen in its entirety, has its distinctive points and 

 potentialities; and within and without are working 

 forces that under similar conditions have only one 

 result, limited in extent, and ^definite in end, so that 

 with mathematical precision they produce effects 

 that follow one another to a certain conclusion. 

 Variation is caused by interference \vith those con- 

 ditions or forces. 



The question of sex, after its first evolution, 

 appears to depend upon the virility of the parent 



* Heredity, and Weismann's germ-plasm, see Addenda. 



t Physiologists would, perhaps more correctly, say that cells are 

 generally nearly of the same size ; but some are larger and some 

 smaller ; and that bulk is caused by increase of either. 



Definite in end in the sense that given certain conditions and forces 

 certain results must follow. 



Sex. Read Professor J. Arthur Thomson's Heredity r , p. 476 ; and 

 Dr. H. C. Bastian's The Nature and Origin of Living Matter, pp. 85, 

 86, 87. So much flows from, what may be poetically called, nature's 

 effort to restore to the egg its normal number of chromosomes. The 

 evolution of the race, all religion, art, science, etc. 



