PHYSIOLOGICAL RELATIONS OF NUCLEUS AND CYTOPLASM 349 



in the perivisceral fluid, accompanied by a nurse-cell having a very 

 large chromatic nucleus, while that of the ^gg is smaller and poorer 

 in chromatin. Astheecro: 

 completes its growth, the 

 nurse-cell dwindles away 

 and finally perishes (Fig. 

 jG). In all these cases 

 it is scarcely possible to 

 doubt that the ^gg is in a 

 measure relieved of the 

 task of elaborating cyto- 

 plasmic products by the 

 nurse-cell, and that the 

 great development of 

 the nucleus in the latter 

 is correlated with this 

 function. 



Regarding the posi- 

 tion and movements of 

 the nucleus, Korschelt 

 reviews many facts 

 pointing toward the 

 same conclusion. Per- 

 haps the most sugges- 

 tive of these relate to 

 the nucleus of the e^s: 

 during its ovarian his- 

 tory. In many of the 

 insects, as in both the 

 cases referred to above, 

 the egg-nucleus at first 

 occupies a central posi- 



g 



n 



Fig. 163. — Upper portion of the ovary in the earw ig /l?/-- 

 Jiciila, showing eggs and nurse-cells. [KoRSCHELT.] 



Below, a portion of the nearly ripe egg {e), showing deuto- 

 plasm-spheres and germinal vesicle {g.v.). Above it lies the 

 nurse-cell («) with its enormous branching nucleus. Two suc- 

 cessively younger stages of egg and nurse are shown above. 



tion, but as the Qgg be- 

 gins to grow, it moves to the periphery on the side turned toward 

 the nutritive cells. The same is true in the ovarian eggs of some other 

 animals, good examples of which are afforded by various coelenterates, 

 ^.^. in medusae (Claus, Hertwig) and actinians ( Korschelt, Hertwig), 

 where the germinal vesicle is always near the point of attachment of 

 the ^gg. Most suggestive of all is the case of the water-beetle Dytis- 

 ciis, in which Korschelt was able to observe the movements and changes 

 of form in the living object. The eggs here lie in a single series alter- 

 nating with chambers of nutritive cells. The latter contain granules 

 which are believed by Korschelt to pass into the ^gg, perhaps bodily, 

 perhaps by dissolving and entering in a liquid form. At all events, 



