142 Animal Life and Intelligence. 



thing and everything. The fundamental assumption that 

 "whereas germ-plasm can give rise to body-plasm to any 

 extent, body-plasm can under no circumstances give rise to 

 germ-plasm, introduces an unnecessary mystery. Biological 

 science should set its face against such mysteries. The 

 fiction of two protoplasms, distinct and yet commingled, 

 is, in my opinion, little calculated to advance our know- 

 ledge and comprehension of organic processes. For myself, 

 I prefer to take my stand on protoplasmic unity and 

 cellular continuity. 



The hypothesis of cellular continuity is one that the 

 researches of embryologists tend more and more to justify. 

 The fertilized ovum divides and subdivides, and, by a con- 

 tinuance of such processes of subdivision, gives rise to all 

 the cells of which the adult organism is composed. It is 

 true that in some cases, as in that of peripatus, as inter- 

 preted by Mr. Adam Sedgwick, the cells of the embryo run 

 together or remain continuous as a diffused protoplasmic 

 mass with several or many nuclei. But this seemingly 

 occurs only in early stages as a step towards the separation 

 of distinct cells. And even if the process should be proved 

 of far wider occurrence, it would not disprove the essential 

 doctrine of cellular continuity. The nucleus is the essence 

 of the cell. And the doctrine of cellular continuity empha- 

 sizes the fact that the nuclei of all the cells of the body 

 are derived by a process of divisional growth from the first 

 segmentation-nucleus which results from the union of the 

 nuclei of the ovum and the sperm. In this sense, then, 

 however late the germinal cells appear as such, they are 

 in direct continuity with the germinal cell from which 

 they, in common with all the cells of the organism, derive 

 their origin. In this sense there is a true continuity of 

 germ-cells. 



Now, it has again and again been pointed out that the 

 simple cell of which an amoeba is composed is able to per- 

 form, in simple fashion, the various protoplasmic functions. 

 It absorbs and assimilates food; it is contractile and 

 responds to stimulation ; it respires and exhibits metabolic 



