THE GERM-PLASM THEORY 79 



determinant-complex of the ectoderm, in the 

 form of an inactive accessory idioplasm, which 

 is excited to regenerative activity by the stimulus 

 of wounding, and that, in the same way, the cells 

 of the endoderm are equipped with the whole 

 determinant-complex of the endoderm." Vol. 

 ii. 5. 



Let us again pause and consider the enormous 

 complexity of the cellular mechanism postulated 

 by this theory. Each cell, or, at least, a very large 

 number of the cells, in an organism like hydra, 

 must contain not merely the substances required 

 for the carrying on of its own activities, but also 

 the highly complex determinants necessary for 

 the rebuilding of the body, should an accident 

 occur and the cell in question be called upon to 

 take up that duty. Remember also that this is an 

 accident which may not happen to more than one 

 out of a million cells so provided. Surely this is a 

 very wasteful expenditure of the highly organized 

 germ-plasms and its determinants. Of course, the 

 complexity of the theory is not necessarily an 

 argument against it. It is not impossible for the 

 tiny sphere of the germ-cell to be packed with a 

 multitude of independent fragments. Nageli 

 calculated that a " moneron " .6mm. in diameter 

 might contain a 100 billions of vital particles, if 

 its dry substance be taken as ten per cent, of the 

 whole. Professor M'Kendrick says : 



" Small as the reproductive body formed by 

 the fusion of the male and female elements is, it is 

 still large enough to contain millions of organic 



