Manchester Memoirs, Vol. xliii. (1899), No. \%. 3 



the parent or parents. The power of differentiation is 

 conveniently expressed by the word evolution ; the power 

 of the reproduction of the biological experience of the 

 parent cells apparently inherent in living matter, by the 

 word heredity. 



Coming back now to our simple living molecules we 

 have to recognise in them two methods of breeding, 

 reproduction by mere scissiparity, the living cell dividing 

 itself into two or more, or reproduction by differentiation 

 as members of a community resulting in spores, or seeds, 

 or eggs, which seem to contain in themselves the organic 

 memory, if I may so express it, of all the phenomena of 

 their descent. The differentiation and division of labour 

 characteristic of the latter mode of reproduction may 

 extend even to a division into separate communities, the 

 co-operation of which is necessary for the reproduction of 

 either community as a whole; in other words into the evolu- 

 tion of the sexes as in monoecious plants and the higher 

 animals. It will be sufficient for the present to sum up 

 these two methods as reproduction by scissiparity and by 

 eggs, merely remarking that reproduction by true seeds or 

 eggs is a more advanced stage of differentiation, or com- 

 munal division of labour, as compared with reproduction 

 by spores, just as reproduction by spores is an advance on 

 reproduction by mere scissiparity, and may be spoken of as 

 a first attempt at communal work. But here we must 

 recognize that reproduction by scissiparity implies merely 

 the reproduction of the individual cell, while reproduction 

 by spores implies the reproduction of the primitive tribe, 

 and reproduction by seeds or eggs the reproduction of the 

 highly organised society. Both the simpler methods have 

 been observed in the lowest forms of life. Thus, anthrax may 

 grow as mere mycelium by cell division or, if cultivated 

 under appropriate conditions, it will produce spores which 



