80 FECUNDATION; HETEROGAMETES. 
former. These plasmic rings or diaphragms communicate with each 
other by plasmic strands or bridges. In the plasmic rings are located 
the rounded chloroplasts, pyrenoids and the nuclei. Of the latter the 
number in each ring varies from 3 to 20 in var. braunzd and from 1 to 4 
in var. crassisepta (Fig. 27, A). 
In those cells in which spermatozoids are developed the nuclei 
undergo four or five karyokinetic divisions,’ so that ultimately about 
300 small nuclei are present in each band (Fig. 28, Ato F). During 
these divisions the pyrenoids disappear, and the chromatophores 
undergo several divisions and assume a pale, yellowish-brown color. 
Fie. 27.—Cell-cleavage leading to formation of egg-cells in Spheroplea braunit.—( After Klebahn.) 
A, outer view of a protoplasmic ring of a vegetative cell, showing chromatophores, pyrenoids and nuclei. 
B, portion of an odgonium showing frothy natbre of protoplasm and early stages of cleavage. 
C, small portion of oégonium, showing irregular protoplasts resulting from cleavage, which contain 
several nuclei and pyrenoids. 
The plasmic rings up to this time retain their original form. Now 
the cytoplasm segments into numerous protoplasts, the spermatozoids, 
in such a manner that each spermatozoid receives only one nucleus 
(Fig. 29, I, J, K, L). The mature spermatozoids (var. crassésepta) 
are as a rule spindle-shaped, being smaller at the anterior end, which 
bears the two cilia. Near the middle lies the very small and densely 
staining nucleus (Fig. 29, L). Kny in his Wandtafel, cx, figures 
four or five yellowish chromatophores in each spermatozoid. 
The processes leading to the formation of the egg-cells show a 
marked difference from those taking place in the antheridium. Even 
1 For details of karyokinesis see Klebahn, ’g99. 
