VIII RECRESCENCE IN DIFFERENT DEGREES 397 



the more highly-organised species must always contain in 

 itself the sum of the most essential of the tendencies of 

 growth of the lower, and must be capable of exhibiting those 

 tendencies. 



Thus, as it seems to me, as by individual development, so 

 also by recrescence, complete proof of the truth of my theory 

 of the organic growth of the living world is supplied. 



I must make my argument complete by entering further 

 into details. 



The reason why the power of recrescence is greater in 

 simple organisms than in more complex, why in general it is 

 greater in proportion as the grade of organisation is lower is 

 obvious : for, as was stated above, the power of recrescence 

 depends upon the retention by the cells of the organism of the 

 properties of the germ-cell, or mother-cell. The lower we 

 descend in the scale of multicellular animals and plants, the 

 more these approximate to colonies of unicellular beings — the 

 more is each of the component cells similar or equivalent to 

 every other, similar or equivalent to the germ or mother-cell. 

 Therefore recrescence in a simple cell-colony such as consti- 

 tutes any of the lowest multicellular plants or animals is not 

 surprising — it almost explains itself that every cell of such a 

 colony can grow again into the whole. Every cell in such 

 colonies possesses every capacity required for independent 

 life. The higher the grade of the organism, that is, the 

 greater the degree to which division of labour, the differentia- 

 tion of the formative tendency into various directions, has 

 been carried, so much the less is this the case, so much the 

 more do its cells depend on other cells, its parts on other 

 parts, finally on central organs, without whose aid they can- 

 not live and multiply, and therefore cannot produce re- 

 crescence. Again, the power of recrescence is greater in 

 youth than in age. It is greatest indeed in the embryonic or 

 foetal condition, as is shown, for instance, by the development 



