114 



THE GERM-CELLS 



than the Q.gg itself, and contains a large, irregular nucleus, rich in 

 chromatin (Fig. 57). The egg-cell rapidly grows, apparently at the 

 expense of the nurse-cell, which becomes reduced to a mere rudi- 

 ment attached to one side of the egg and finally disappears. There 

 can hardly be a doubt, as Korschelt maintains, that the nurse-cell is 

 in some manner connected with the elaboration of food for the grow- 

 ing egg-cell ; and the intensely chromatic character of the nucleus 

 is well worthy of note in this connection. 



Somewhat similar nurse-cells occur in the insects, where they have 

 been carefully described by Korschelt. The eggs here lie in a series 

 in the ovarian "egg-tubes" alternating with nutritive cells vari- 



Fig. 5Y. — Egg and nurse-cell in the annelid, Opiuyotiocha. [Korschelt.] 

 A. Young stage, the nurse-cell («), larger than the egg {o), B. Growth of the ovum. C. Late 

 stage, the nurse-cell degenerating. 



ously arranged in different cases. In the butterfly Vanessa, each 

 egg is surrounded by a regular follicular layer of cells, a few of 

 which at one end are differentiated into nurse-cells. These cells 

 are very large and have huge amoeboid nuclei, rich in chromatin 

 (Fig. 58, /4). In the ear-wig, Forfiada, the arrangement is still more 

 remarkable, and recalls that occurring in OphryotrocJia. Here each 

 egg lies in the egg-tube just below a very large nurse-cell, which, 

 when fully developed, has an enormous branching nucleus as shown 

 in Fig. 115. In these two cases, again, the nurse-cell is characterized 

 by the extraordinary development of its nucleus — -a fact which 

 points to an intimate relation between the nucleus and the metabolic 

 activity of the cell.^ 



In all these cases it is doubtful whether the nurse-cells are sister- 



1 See p. 254. 



