THE OKGANIC CELL 
41 
of which the egg is closely attended by a nurse-cell which is 
attached to its side. In the case of the Annelid Ofhryotrocha 
the nurse-cell is at first considerably larger than the egg itself, 
possessing a large nucleus loaded with chromatin. While 
the egg-cell grows at a great rate, there is a corresponding 
rapid diminution in the size of the nurse-cell, which, becoming 
a mere rudiment, finally disappears. From this it is evident 
there is a very close association between the nurse- cell and 
the growing egg. 
The observations of Wheeler on another form are of special 
interest. In this case the egg-cell is accompanied by two 
A B C 
Egg and Nurse-cell in the Annelid, Ophryotrocha. (Korschelt.) 
A. Young stage, the nurse-cell at (N) is larger than the egg (O). B. The 
ovum growing. C. Degeneration of the nurse-cell (N). 
nurse-cells, one placed at either end. Quoting from Wheeler, 
4 these cells fuse bodily with the egg, one having something 
to do in forming the vacuolated cytoplasm at the animal 
pole, the other in forming the granular cytoplasm at the 
vegetable pole.’ (‘ The Maturation, Fecundation, and early 
Cleavage in Myzostoma .’ ) This determination of the polar 
axis maintains in the ripe ovum. 
In the earwig Forficula the egg-cells are accompanied 
by large nutritive nurse-cells, these cells possessing well-defined 
nuclei richly endowed with chromatin. 
From the above examples one is naturally drawn to the 
conclusion that the nurse-cell greatly assists in, if it is not 
wholly responsible for, the elaboration of the cytoplasm of 
