66 Vitality and Oi-ganization of Protoplasm. 



phyletic evolution, and in proportion, moreover, as the embryo repre-- 

 sents a more or less advanced stage towards the complete reproduction 

 of the adult organism. The germ-plasm itself must at every stage of its 

 evolution necessarily possess a more or less complex chemical organi- 

 zation in proportion as it is derived from a more or less complexly de- 

 veloped organism, , 



To our vision ontogenetic evolution assumes the aspect of a process 

 giving rise to different definitely grouped parts of the evolving sub- 

 stance, and it takes a definitely regulated course within the portion of 

 our field of vision occupied by the developing substance. Our conclu- 

 sions regarding the specific potencies actuating these visible changes 

 have to be inferred from what we see arising here and there within the 

 sphere of the evolving plasm. However accurate our observations and 

 descriptions of such spatial changes may be, it is clear that the infer- 

 ences and interpretations based upon them, regarding the agencies 

 actuating the changes, and also regarding the interdependence of the 

 changes seen to take place in different parts of the evolving plasm; that 

 these inferences and interpretations are of a different explanatory order 

 from that of mere description. To the extremely difficult solution of 

 these ontogenetic questions of special potencies, and causal dependence 

 of localized changes, experimental ontology is supplying the most effi- 

 cient and instructive means. 



But it must not be forgotten, that the final, predetermined result and 

 outcome of all the divers and complex changes is the exact reproduction 

 of the adult organism from which the germ-plasm was derived. The 

 sundry divers changes form part of one and the same ontogenetic pro- 

 cess. Or as Driesch more specifically expresses it : "Despite relative 

 self-differentiations something unitary is achieved." The entire onto- 

 genetic evolution which we see running its course in space and time 

 with such intricate formative manifestations is essentially a unitary pro- 

 cess, predetermined in its minutest details in the specific chemical con- 

 stitution and in the chemical potencies of the germ-plasm ; attaining 

 its final goal in the definite organization of the reproduced adult organ- 

 ism as an indiscerptible whole. There is here at work no sort of struggle 

 for supremacy of separate elementary units, and no automatic co-opera- 

 tion of the same. From its initial stage to its completion the onto- 

 genetic process consists in the harmonious, gradual reintegration of a 

 specific chemical fragment under complemental assimilation, until it 

 has effected the reconstitution of the whole of which it is a fragment; 

 and which whole is then visually revealed to us as the complex adult 

 organism. 



If a morphologically undifferentiated fragment of the egg of a 

 frog can reproduce an entire, highly differentiated, embryo, it is almost 

 self-evident, that, in what may be rightly called the chemical constitu- 

 tion of the egg-plasm, must lie the power to evolve the eminently com- 

 plex structure and form of the adult frog; that, therefore, this emi- 

 nently complex structure and form represents to us the perceptible out- 



