374 SUMMARY OF CURRENT RESEARCHKS RELATING TO 



from the oogonia. Their differentiation occurs in the zone of differentia- 

 tion. One of the cells of each rosette enlarges and becomes an oocyte, 

 or more than one may do so. The others retain more of their earlier 

 characteristics and become nurse cells. Although the strands which 

 connected the cells in a rosette disappear, the descendants of a single 

 oogonium may still lie determined because of the presence of deeply 

 staining rings between the cells. Granules appear near the nucleus of 

 oocytes shortly after their differentiation ; they are subsequently distri- 

 buted throughout the ecrg cytoplasm ; they appear to be mitochondrial 

 in nature, and to arise from or under the influence of the nucleus. 



The ovarioles of Gamponohis consist of four distinct regions : (1) a 

 terminal filament : (2) a terminal chamber ; {?>) a zone of growth free 

 from bacteria-like rods ; and (4) the posterior part, in which the oocytes 

 are arranged in a linear series, are accompanied by nurse cells, and are 

 surrounded and later invaded by the bacteria-like bodies. These occupy 

 definite regions of the ovariole. They are absent entirely from the 

 terminal filament, terminal chamber and first zone of growth. In the 

 rest of the ovariole they occur everywhere except in the nurse cells. 

 The oocyte is at first free from them,. but later is invaded by them and 

 almost completely filled. The rods are arranged at first in bundles, 

 Imt are afterwards scattered. As the oocyte increases in size and yolk- 

 formation proceeds, they gradually disappear iintil none are visible 

 except near the periphery in the posterior region. Secondary nuclei 

 appear near the oocyte nucleus at an early stage of growth. They 

 increase in number, finally completely surrounding the germinal vesicle. 

 They are afterwards distributed throughout the oocyte, especially near 

 the follicular epithelium. Their origin by budding from the oocyte 

 nucleus, or by the immigration of epithelial cells seems improbable. 

 The conclusion is reached that the oocyte nucleus gives off materials 

 into the cytoplasm which become enclosed by a membrane and develop 

 into nuclear-like bodies. The fate of the secondary nuclei was not 

 determined. 



The chromatin in the oocyte nucleus of Copklosoma f/elechise forms 

 chromosomes at an early stage in the growth period. These chromo- 

 somes unite near their ends in pairs, and then become arranged in a 

 parallel series upon an asterless spindle. Condensation then occurs and 

 an apparently homogeneous oval-shaped mass of chromatin is formed. 

 The number of pairs of chromosomes is eleven or twelve. The germ- 

 line determinant is not the chromatin from an oocyte nucleus, as the 

 author previously stated ; it appears to be a differentiated part of the 

 protoplasm which arises at an early stage near the posterior end of 

 the oocyte. 



The oocyte nucleus of Apanteles has a history similar to that de- 

 scribed for Go^ndosoma ; chromosomes are formed at an early period, 

 fuse in pairs, become arranged upon an asterless spindle, and undergo 

 condensation. Secondary nuclei make their appearance in the almost 

 fully grown oocytes. They are distributed throughout the anterior part 

 of the oocyte, but are entirely absent in later stages. Their origin and 

 fate were not determined. The deeply staining substance at the posterior 

 end of the older oocytes is probably a germ-line determinant. It first 



