432 ELMER L. SHAFFER. 



nuclei surrounded by a small amount of cytoplasm containing 

 mitochondria. As the synaptic period progresses the oocyte 

 grows somewhat in size, chiefly by an increase in the size of the 

 nucleus and a slight increase in the cytoplasmic volume. After 

 the synaptic processes have been completed, the cytoplasmic 

 volume increase rapidly, so that the oocyte becomes over four 

 times its linear size before yolk begins to form. After the cyto- 

 plasmic volume has reached its maximum, the yolk-building 

 process commences and at the end of this period the almost 

 mature oocyte is about three times its linear size at the beginning 

 of the process. This great increase in size is not due to any 

 increase in cytoplasmic volume, but due to the great enlargement 

 of the yolk spherules. It is doubtful whether the cytoplasmic 

 volume increases at all after the beginning of the yolk formation. 

 The ingestion of the nurse-cells by the oocytes in Cicada is 

 perhaps homologous to the ingestion of the cells in the ovaries of 

 other forms, the classical example of which is found in Hydra. 

 As is well known, in Hydra one cell in the ovary grows large by 

 ingesting the other cells in the ovary and becomes the functional 

 oocyte. In Dinophiliis, Conklin ('06) has described the fusion 

 of from 25 to 30 oogonia to form a single large (female-producing) 

 egg. In dona and other Ascidians, the test-cells are ingested 

 by the oocytes and remain in the egg, perhaps aiding in the 

 elaboration of nutrient materials, but are cast out of the egg 

 prior to fertilization. In the ovaries of the certain insects (e.g., 

 Dytiscus) of the type in which the oocytes are supplied with a 

 separate group of nurse-cells, the process of absorption of the 

 nurse-cells as the oocyte grows has been often described. Kor- 

 schelt ('86) has described in the ovaries of Notonecta and Redumus 

 a disintegration of nurse-cell nuclei in the nurse chamber through 

 the action of the oocytes, with the production of a central space, 

 " Plasmatische Raum," in the nurse chamber, which is free from 

 nuclei. Foot and Strobell ('n) have also described a similar 

 plasmatic area free from nuclei in the ovaries of Protenor, but 

 are not inclined strongly toward Korschelt's view that in this 

 region the nurse cells disintegrate and furnish nutriment for the 

 oocytes. In Cicada a study of Figs. 34, 45, 71, 72 will show that 

 there is no doubt that Korschelt's view is correct, for, not only 



