32 THE EVOLUTION THEORY 



vidual from definite cells — the reproductive cells — with or without 

 sexual differentiation, but from other cell-groups also, these must 

 contain the whole complex of determinants appertaining to the 

 reconstruction of the organism, and we have to ask how this is 

 reconcilable with the differentiation of a multicellular organism, 

 whose different kinds of cells depend, according to our interpretation, 

 on the fact that they are controlled by different determinants. 



Obviously, there is only one way out of this difficulty, and it 

 is the one we have already indicated, that although the diffuse 

 regenerative capacity which we have just alluded to occurs in species 

 which exhibit gemmation, this does not exclude the control of a cell 

 by a specific determinant ; other determinants may be contained in 

 the cell, in a state, however, in which they do not affect it, that is, 

 in an inactive or latent state. 



Thus we arrive in this way also at our earlier assumption that 

 an inactive accessory-idioplasm is given to all, or at least to many 

 cell -generations. Only among plants must this necessarily be complete 

 germ-plasm, and among the lower plant-forms, as in Caulerpa among 

 the Algse, in 3Iar chant ia among Liverworts, it must be assumed to 

 be present in nearly all the cells, according to the experiments 

 in regenei-ation made by Reinke and Vochting. But in multicellular 

 animals which develop from two different germinal layers equipped 

 with a different complex of determinants budding arises from a 

 combination of at least two different kinds of cells, and we must 

 only ascribe to each of these its own peculiar determinant-complex 

 as regeneration-idioplasm. Higher plants show us that well-marked 

 power of budding is not necessarily associated with a high regenerative 

 capacity, the histologically specialized cells among them will contain 

 no inactive germ-plasm, because they do not need it. But in animals 

 the power of budding is probably always combined with high re- 

 generative capacity, as is shown by the Polyps and Medusoids above 

 all, and in a different way by the Ctenophores, which exhibit no 

 budding and at the same time a very slight regenerative capacity, 

 although they possess an organization scarcely higher than that of 

 the HydromedusEe. In the Ctenophores each of the first segmentation- 

 cells, when artificially separated, yields only a half- embryo, and we 

 may conclude from this that it contains no complete germ -plasm in an 

 inactive state, or at least very little, and certainly not a sufiicient 

 quantity to make it readily regenerative. 



Undoubtedly, however, the regenerative capacity occurs apart 

 from the capacity for budding, yet this in no way contradicts the 

 theory. As we have seen, a high regenerative capacity is to be 



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