706 THE AMERICAN NATURALIST [Vol. LI 



and other nuclear substances into the cytoplasm occurs 

 during the maturation divisions of the egg, but this period 

 may be neglected in this connection, since the organiza- 

 tion with which we are concerned is already established 

 before maturation takes place. Even when the nuclear 

 membrane is intact, substances undoubtedly pass in and 

 out of the nucleus much as they do through the cell mem- 

 brane, and as in the latter, the nuclear membrane may 

 change in permeability at different times, these changes 

 being due to chemical processes taking place within the 

 nucleus or in the cytoplasm. Such changes occur more 

 often during periods of cell activity than at other times 

 and thus we should expect pronounced interaction 

 throughout the growth period of the oocytes. 



Besides gradual, and for the most part invisible, inter- 

 changes of this sort there may be actual transference of 

 visible masses of chromatin from the nucleus to the 

 cytoplasm. These chromatin granules that escape into 

 the cytoplasm have been called "chromidia" and are sup- 

 posed to play a part in cytoplasmic differentiation. 



A peculiar process of interchange by means of sec- 

 ondary nuclei is exhibited by certain insects, especially 

 Hymenoptera.-^ This process has been studied most 

 carefully in the carpenter ant, Componotiis herculeanus 

 var. pennsylvanica (Fig. 11). At an early stage in the 

 growth of the oocyte small vesicles containing a few 

 granules of chromatin appear near the oocyte nuclei. 

 These ''secondary nuclei" appear to arise as buds from 

 the primary nucleus, but no one has yet actually observed 

 their formation in this way. It has also been suggested 

 that they may be epithelial cells that have invaded the 

 oocyte, but this seems very improbable. The writer has 

 reached the conclusion that they consist of nuclear ma- 

 terials that have been given off into the cytoplasm and 

 have there become enclosed by membranes which give 

 them a nuclear-like appearance. As the oocyte increases 



28Blockmann, 1886, Festsch. nat.-med. Verein zu Heidellerg ; Buchner, 

 1913, Biol. Centrlbl., Bd. 33; Hegner, 1915, Journ. Morph., Vol. 26. 



