252 University of California Publications in Zoology [Vol. 16 



la vesiciile et la earyosome, uu leger coagulum eosinopliile de chroma- 

 tine peripherique." In the early prophases, however, there is a verj' 

 graniilar layer next to the membrane (pi. 18, fig. 4; pi. 20, figs. 40, 44). 

 The granules may be large and deeply stained, with stainable lines 

 connecting some- of them with the karyosome, or they may be finely 

 granular, with or without visible lines (pi. 20, figs. 40, 44). Only 

 rarely are the granules to be found which take the chromatin stain or 

 retain it after destaining. However, this may be due to the fact that 

 in general the chromatin is so diffuse that all the .stain comes out by 

 the time the cytoplasm and karyosome are sufficiently destained. 



Coincident with the elongation of the karyosome in division, the 

 peripheral net becomes loose in structure, collects at one side between 

 the membrane and karyosome (pi. 20, figs. 39, 44), and finally takes 

 up its position on one side of the karyo.some, becoming more fibrillar in 

 appearance as the elongation of the karyosome progresses (pi. 19, figs. 

 38, 45). The connection with the karyosome may take place after the 

 latter has become dumb-bell shaped (pi. 18, figs. 2. o), but its position 

 is always on one side until the late jjrophase, at which time it is mid- 

 way between the two chromatic polar masses, which are now connected 

 only by the central spindle (pi. 20, fig. 52). 



In the process of reorganization of the nucleus, which may begin 

 in the late anaphase (pi. 20, fig. 37), there is an extrusion of chromatin 

 netwoi'k from the region between the chromatic polar mass and the 

 chromosome mass to a position around the nuclear membrane (pi. 18. 

 figs. 12. 15: pi. 20, figs. 51, 53, 57). 



The spindle as it appears in the metaphase, with its large polar 

 masses made \ip of plastin, chromatin, and centrioles, its eight distinct 

 spindle fibers upon each of which is a chromo.some, all of which are in 

 a regular equatorial plate, and its central spindle, is characteristic in 

 its formation. In the early stages there is an elongation and bending 

 of the karyosome, with a gradual decrease in size of the part connecting 

 the two separating karyosome ends or masses, and an entrance into the 

 angle between the polar masses of the peripheral net. The centriole 

 divides in the early elongation stage of the karyo.some (pi 20, fig. 62) 

 and. as elongation continues, one centriole is to be found in each polar 

 mass with the central spindle in the gradually decreasing region 

 between the two chromatic polar masses. From the plastin of the 

 chromidial net, which is evidently from both the peripheral chromatin 

 and the karyosome (cf. pi. 20, figs. 38. 45. 60), the eight spindle fibers 

 are formed. 



