THE VITAL PHENOMENA OF THE CELL 213 



the internal vesicle begins to shrink up and loses its nuclei, 

 which pass into the protoplasm outside. Finally it is quite dis- 

 solved. Brandt has observed that this nuclear multiplication 

 varies according to whether isospores or anisospores are formed. 



From the whole process R. Hertwig and Brandt draw the 

 following conclusion, which is certainly correct : that the nuclei 

 which function in the formation of zoospores, and which occur in 

 the central capsule, at first but sparsely, but which gradually 

 increase in number, are derived from the substance of the internal 

 vesicle (nuclear corpuscles). "This explanation," remarks R. 

 Hertwig, " leads me to adopt a theory of nuclear multiplication 

 which differs fundamentally from the generally accepted one, and 

 which is not supported by any observations which up till now have 

 been made in animal or vegetable histology. For if we try to 

 explain this process histologically, we must conclude not only that 

 nuclei can multiply by division or budding, but that they may 

 be produced by the nuclear substance of a nucleus multiplying 

 itself by division, the portions thus produced making their way 

 into the protoplasm to which they belong, and there developing 

 into independent nuclei. Hence such a cell containing many 

 nucleoli may be regarded as potentially multinuclear, just as a 

 multinucleated cell may be regarded as potentially multicellular ; 

 and thus the gradual transition between individual cells, and the 

 groups of cells which are derived from them by division, is by 

 these intermediate stages rendered easier than it would otherwise 

 be." 



The extraordinary phenomena of nuclear multiplication, observed by Fol 

 (VI. 20), Sabatier, Davidoff (VI. 87), and others, in rather young immature eggs 

 of Ascidians, and which have been shown to be connected with the develop- 

 ment of follicle cells, may be mentioned here. Compare also the similar 

 processes observed by Schiifer (VI. 65a) in young mammals. 



IIL Various Methods of Cell Multiplication. 



1. General Laws. 



In addition to the process mentioned in the last section under 

 the names of nuclear segmentation, direct nuclear division, and 

 endogenous nuclear formation, cell multiplication may assume 

 very various appearances according to the way in which the 

 protoplasmic body behaves during division. Before classifying 

 the various kinds of cell multiplication, it is necessary to mention 



