/^ 



z//-^_ 



-/ 



THE BEGINNINGS OF LIFE. 



95 



'■^'^^Ps as 

 '-^ into a 

 the 





J 



^anie. 



\ 



) reptile^ 

 ^ionofan 



developiiijj 





trariwise, the aggregate is made by incident actions to 

 take a new form, its forces must tend to remould the 

 units into harmony with this new form. And to say 

 that the physiological units are in any degree so re- 

 moulded as to bring their polar forces towards equi- 

 librium with the forces of the modified aggregate, is 

 to say that when separated in the shape of reproduc- 



pi-, - tive centres, the units will tend to build themselves 



up into an aggregate modified in the same direction/ 

 Amongst simple organisms almost any part of the sub- 



F 



stance which separates^ or is separated, from one of them 



ment which fe 

 These ph 



en: 



-L^w of Her; is capable of developing into a similar simple organism, 

 rareful zmk But as organisms grow more and more complex in their 

 nirably rendeit structure, so we find that a difference arises in the re- 

 productive powers of different tissues — till at last the 

 form we ir: capacity to reproduce the entire organism (either with- 

 out fertilization or only after this has occurred) becomes 



^ Bringing tli£ 



t 



iological unit 



Ml i^^jiiseke rcstricted to the morphological units which are produced 



-e; so, 



on 



Liiism IS 



<;$ some 



tk 



mod: 



in special organs i. How much this restriction of the 



reproductive function is due to a general specialization 

 is obvious from the fact that it is most marked where 



complexity of organization attains its maximum. Com- 

 plexity of structure necessarily carries with it complexity 

 ;t act anui^" ^^ function, and in proportion as distinct functions 



crfif 



olar'iUes of'' 



;•(( 



on 



f n 



each unit' 



, -J * The necessity for the fertilization of some of these reproductive ele- 



C^Cn ments, and the evolution of sexual differences amongst the animals and 



nthifln f P^^^^^ amongst which this necessity obtains, is merely a superadded 



ate ii^to ^ 



:F 



lariti^^' 



jj)( complexity— a difference of degree and not of kind. The fundamental 

 . phenomena of reproduction are essentially similar in sexual and sexless 

 •^ organisms. (See Spencer's * Principles of Biology/ vol. i. pp. 218-223.) 



l.i-P 



.25 



6. 



