Mode of Inheritance of Adaptive Characters. 65 



remnant of the germinal power persists, and this must be 

 very considerable in those cases where there is regeneration 

 of a whole limb. A point in favour of the view of a migra- 

 tion of the primary germ cells to their position in the 

 embryo, is the very localised position of the reproductive 

 organs, and it is difficult to understand, on a theory of the 

 origin of germ cells from the embryo, how they could retain 

 their primitive character and always come to lie in the same 

 position, unless they constituted a kind of meristem, from 

 which all the other tissues are budded off. 



Ever}^ cell, in the Metazoon or the Metaphyte, must be 

 considered as a separate organism, which is kept along the 

 right lines of development partly by association with its 

 fellows. The development and specialisation of the com- 

 pound individual would depend on the resultant of the 

 individual tendency of each cell to develop along lines 

 inherited from its forerunners, and the help or restriction 

 imposed upon it by the other cells of the group in relation 

 to the total environment. There will thus be, as in " the 

 struggle of parts " suggested by Eoux, an adaptation of the 

 different parts to one another, through a struggle for exist- 

 ence in their mutual adjustment to their surroundings. A 

 change in one cell will affect the neighbouring cells, and cells 

 at a distance, by transmission of stimuli and by means of 

 alteration in the nutrition and the production of chemical 

 bodies. The development will be governed partly by the 

 symbiosis, which will be the more complex according to the 

 complexity of the creature. In this connection should be 

 remembered the effect of symbiosis on specific development 

 in lichens, as also the effect of external conditions on plant 

 rudiments and developing embryos. But there is also the 

 common reservoir of sap, lymph, or blood, which is the chief 

 environment of the cell community. From it the cells 

 receive their nourishment, and into it they pass their pro- 

 ducts of metabolism, and alteration in it is known to be 

 a source of much change amongst them. All the cells of the 

 group are derived from one initial cell; and their degree of 

 specialisation depends on the amount of divergence in their 

 metabolism from that of their mother. They all carry the 



VOL. XVI. H 



