188 JOHN E. S. MOORE. 



mass, obviously homologous to the archoplasm (" Neben- 

 kern''), concentrically gathered about a very distinct pale 

 zone, the ''medullary corpuscle" of van Beneden, which 

 encloses one or two large and beautifully defined central 

 bodies (figs. 17—20). 



A delicate radiation spreads from the whole sphere to the 

 periphery of the cell. This is not concentric with the radii of 

 the archoplasm, nor are these latter centred towards the 

 enclosed body or bodies, but to the " medullary corpuscle" as 

 a whole. 



Thus it is seen that the radial conditions apparent in the 

 spheres of Ascaris, Helix, and the undifferentiated genital 

 ridge of the salamander, repeat themselves in the leucocytes of 

 the last. 



In certain leucocytes I have often observed the archoplasm 

 expanded like a fan, whose apex is usually turned towards the 

 nuclear elements, and crowned by a distinct and stained 

 central body from which radiations pass in all directions 

 (fig. 20). 



This condition appears to me to be strictly analogous to that 

 in figs. 13, 14. Whatever method may have been used with 

 respect to the leucocytes, in the majority the archoplasm is 

 with difficulty or not at all forthcoming, the central body 

 or bodies usually appearing related to a simple radiation 

 extending at once from them to the circumference, the condi- 

 tion being closely similar to that I have represented in the 

 cells of the genital ridge in fig. 22 ; and both appear to present 

 structural relationships identical with those figured by Biirger 

 in the cell-bodies of the Nemertian " Leibesfliissigkeit."^ 



From these dififerences of appearance in the archoplasm it is 

 in the highest degree probable that the leucocytes present a 

 similar archoplasmic metamorphosis to that I have alluded to, 

 and shall presently describe in detail, in the cells constituting 

 the genital ridge, and which is so conspicuous, according to 

 Platner, in the spermatocytes of Helix. The existence of the 

 "Nebenkern'' (archoplasm) in the cells of the embryonic 

 ' ' Anatomischer Auzeiger/ 1891, p. 484. 



