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IVATASE. 



[Vol. IV. 



identical by the means of observation at our disposal. Thus, 

 instead of inferring function from structure, we infer structure 

 from function, and conclude that wherever we detect a differ- 

 ence in function the protoplasmic structure must be different 

 also. When, therefore, we speak of the analysis of nuclear 

 substances we do not speak from actual knowledge of the sub- 

 stances thus analyzed, but from purely scientific reasoning. 



A. Centre of Archoplasm. 



B. Extra-nuclear archoplas- 



mic filaments. 



C. Cytoplasm. 



D. Interzonal archoplasmic 



filaments. 



E. Intra-nuclear archoplas- 



mic filaments. 



F. Remnant of nuclear cav- 



ity filled with nuclear 

 fluid. 

 3f. Limit of the original 

 nuclear cavity, sharply 

 separated from the 

 surrounding cytoplasm. 

 n, n'. Two daughter chromo- 

 some bands. 



Figure VI. — Asterias. 



It is probable that during cleavage, the original nuclear sub- 

 stance may undergo a series of molecular changes, and split up 

 into a number of protoplasmic substances, each of a different 

 molecular structure, and that as a final result of this chain of 

 metamorphoses different kinds of tissue-cells come into exist- 

 ence.^ In short, different morphological stages of the develop- 

 ing ovum may be considered as so many different molecular 

 conditions of the protoplasm. And perhaps the molecular 

 constitution of a dividing ovum in its earlier stage may differ 

 more from that of the later larval stage, than two organisms 



^ See in this connection, Roux: Bedeuiung der Kerntheilungsfiguren. 1883. 



