LYCASTIS OUADRAT1CEPS. 



377 



eccentric, and the nuclear membrane is sharply defined ; the 

 chromatin, at first scanty (Fig. 4), becomes more abundant in 

 the older eggs (Fig. 3). It has the form of granules rather than 

 threads and sometimes part of it has a peripheral arrangement 

 (Fig. 4). . 



The nucleolus at all stages of the ovum observed is a dense 

 refractive spherical body, measuring from 10 microns in the 



x n.c. 



Fig. 3. Transverse section, middle region, stained with hsemalum and eosin. Sec- 

 tion passes through an ovum (0) and its nucleus. Bunches of sperm cells (s) seen dis- 

 tributed throughout the ccelom. The nerve cord [n.c.) and transversal muscles ex- 

 tending from it right and left ; d.v., v. v., dorsal and ventral blood vessels ; n.t., ne- 

 phric tubule cut across in several places; in., intestine. Amibocytes in ccelom. 

 X 100. 



young eggs up to 22 microns in the mature ones. It is eccen- 

 tric in position, and remarkable for its opacity, being of a brown 

 color by transmitted light and almost white by reflected light. 

 Owing to the strong contrast in color to the ovum it serves as a 

 useful landmark in the enumeration of ova. 



The youngest ova and some of the mature ones are accompa- 

 nied by a group of "nurse-cells." The condition, however, is 



