THE CELL-THEORY 2/7 



We cannot conclude better than by concisely repeating the points 

 to which we have attempted to draw attention in the course of the 

 present article. 



\^'e have endeavoured to show that life, so far as it is manifested 

 by structure, is for us nothing but a succession of certain morphological 

 and chemical phenomena in a definite cycle, of whose cause or causes 

 we know nothing ; and that, in virtue of their invariable passage 

 through these successive states, living beings have a development, a 

 knowledge of which is necessary to any complete understanding of 

 them. It has been seen that Von Baer enunciated the law of this 

 development, so far as the organs are concerned ; that it is a continually 

 increasing differentiation of that which was at first homogeneous ; and 

 that Caspar Friedrich Wolff demonstrated the nature of histological 

 development to be essentially the same, though he erred in some 

 points of detail. We have found Schwann demonstrating for the 

 animal, what was already known for the plant — that the first histo- 

 logical differentiation, in the embryo, is into endoplast and periplast, 

 or, in his own phrase, into a '' nucleated cell ; " and we have endeavoured 

 to show in what way he was misled into a fundamentally erroneous 

 conception of the homologies of these two primitive constituents in 

 plants and animals — that what he calls the " nucleus " in the animal 

 is not the homologue of the " nucleus " in the plant, but of the 

 primordial utricle. 



W^e have brought forward e\idence to the effect that this primary 

 differentiation is not a necessary preliminary to further organization — 

 that the cells are not machines by which alone further development 

 can take place, nor, even with Dr. Carpenter's restriction (p. 737), are 

 to be considered as " instrumental " to that development. We have 

 tried to show that they ^e not iristrumentSj but indications — that 



they arejTO__m ore the producers of the vital_j)henomena than the 

 shells scjJtteredJn orderly lines along the sea-beach are the instruments 

 by which the gravitatiye force of the moon acts upon the ocean. Like 

 these, the cells_mark only where the vital tides have been, and how 

 they haye acted. 



Again, we have failed to discover any satisfactory evidence that 

 the endoplast, once formed, exercises any attractive, metamorphic, or 

 metabolic force upon the periplast ; and we ha^•e therefore maintained 

 the broad doctrine established by Wolff, that the vital phenomena are 

 not necessarily preceded by organization, nor are in any way the result 

 or effect of formed parts, but that the faculty of manifesting them 

 resides in the matter of which living bodies are composed, as such — 



