RErRODUCTION. II7 



one explanation of the phenomena to the exclusion of the 

 rest. 



e. Law of Quatrcfagcs. — From the phenomena of asexual 

 reproduction in all its forms, M. de Quatrefages has de- 

 duced the following generalisation : — 



" The formation of new individuals may take place, in 

 some instances, by gemmation from, or division of, the 

 parent being; but this process is an exhaustive one, and 

 cannot be carried out indefinitely: when, therefore, it is 

 necessary to insure the continuance of the species, the sexes 

 must present themselves, and the germ and sperm must be 

 allowed to come in contact with one another." 



It should be added that the act of sexual reproduction, 

 though it insures the perpetuation of the species, is very 

 destructive to the life of the individual. The formation of 

 the essential elements of reproduction appears to be one of 

 the highest physiological acts of which the organism is cap- 

 able, and it is attended with a corresponding strain upon 

 the vital energies. In no case is this more strikingly exhib- 

 ited than in the majority of insects, which pass the greater 

 portion of their existence in a sexually immature condition, 

 and die almost immediately after they have become sexually 

 perfect, and have consummated the act whereby the per- 

 petuation of the species is secured. 



Thus, as pointed out by Dr Carpenter, and strongly in- 

 sisted upon by Mr Herbert Spencer, we are to regard sex- 

 ual reproduction as being directly antagonistic to nutrition. 

 This brings us to the further law that the life of an animal 

 whilst sexually immature is generally associated with active 

 growth ; but that when once the generative expenditure has 

 commenced, the nutritive powers can rarely do more than 

 maintain the ^orgajpism in statu quo, whilst they may even 

 fall short of this. If we regard the asexual methods of re- 

 production as being merely forms of growth, we can readily 

 understand how it is that zooidal multiplicatioi^^nerally 

 excludes sexual reproduction for a time. The ^ffe, how- 



