8 Vitality and Organization of Protoplasm. 



To answer these questions, even when the phyletic factors necessarily 

 involved are left out of consideration, taxes the ingenuity of biologists 

 to the utmost. Conceived as being itself an elementary organism, the 

 germ-cell, like other elementary organisms, can consistently be expected 

 to reproduce by self -division its own likeness only ; and not, as is actually 

 the case, a morphologically most diversified and functionally utterly 

 dissimilar progen3^ Biologists, who regard the germ-cell as a genuine 

 self-dividing elementary organism, have sought to attribute the succes- 

 sive differentiations and developments of its progeny to external causes 

 and conditions, to which in the course of ontogenetic evolution the sun- 

 dry cell-generations are diversely exposed. But, it must be asked, what 

 imaginable external influences could possibly transform during onto- 

 genetic evolution real elementary organisms, such as the germ-cell and 

 its progeny are supposed to l)e, into muscular fibres, neurons, or merely 

 into liver or lymphatic cells ; these forming, moreover, one and all, inte- 

 grant constituents of a complex organism, whose form and structure are 

 rigorously predetermined? 



To render so inconceivable a process to some extent plausible, the 

 germ-cell is sometimes, despite its alleged elementary nature, hypo- 

 thetically endowed with all manner of latent potentialities, which are 

 believed to be respectively awakened to activity by specifically corre- 

 sponding external incitements. These are then held to give rise, each 

 in its special way, to the development of the sundry definite kinds of 

 cellular beings. And as dormant potentialities of the living substance 

 which constitutes cellular beings are known in some instances to be 

 forced by external influences into undergoing definite normal or ab- 

 normal modes of development, this hypothesis does not prima facie 

 seem altogether fanciful. But in normal ontogenetic evolution no such 

 specifically and adequately diversifying external causes can be detected. 

 The reproduction of adult organisms of all kinds runs its course in essen- 

 tially the same physical medium, and its specific distinctions, and there- 

 with its structual differentiations, are evidently determined by inherent 

 endowments of each special germ ; are in fact, strictly predetermined. 



The contents of the germ-cell, though not differentiated during onto- 

 genetic evolution by external influences, must, however, in some man- 

 ner possess within itself diversified potentialities, which in a suitable 

 medium become then essentially self-evolving. In order to account for 

 such manifoldly evolving endowments, the germ-cell is usually con- 

 ceived as made up of a sufficient assortment of hypothetical vital units, 

 such as gemmules, plastidules, pangenes, micelli, plasomes, biophores, 

 etc., etc. And to the differentiated and differentiating endowments of 

 these hypothetical vital imits are then attributed the diversely evolving 

 characteristics of the cellular progeny. 



But here, under this supposition, another formidable difficulty arises 

 to impede the progress of interpretation. For how docs it come to pass 

 that the original contents of the germ-cell, as an elementary organism, 

 which as such would in all its progeny reproduce only its own likeness; 



