468- ROBERT W. HEGNER 



to be found in the literature. Blochmann ('86) discovered a 

 process of 'budding' in the oocytes of Camponotus Hgniperda 

 resulting in the formation of 'Nebenkerne.' These appear first 

 as small vacuoles lying near the nucleus; later they contain small 

 staining granules and acquire a membrane. The 'Nebenkerne' 

 grow in size and increase in number, while the nucleus of the 

 oocyte becomes smaller. Stuhlmann ('86) described a similar 

 phenomenon in about a dozen different species of Hymenoptera. 

 The oocyte nucleus in all species examined becomes localized 

 near the anterior end; then the small nuclear-like bodies form 

 around it at its expense. The time of their production varies 

 in the different species; in some they appear in the very young 

 eggs; in others not until a much later stage has been reached. 

 Sometimes they fuse to form a large 'Dotterkern' lying at the 

 posterior pole of the egg; or they may remain separate and later 

 become scattered. Paulcke COO) also noted nuclear-like bodies 

 near the oocyte nucleus of the queen bee, and Marshall ('07) 

 has likewise found them in PoHstes pallipes. In this species 

 the nuclear-like bodies form a single layer around the nucleus; 

 later they come to lie near the periphery of the oocyte and 

 finally disappear. Loewenthal ('88) has described what appears 

 to be chromatin in the cytoplasm of the egg of the cat, and an 

 ehmination of chromatin was noted by van Bambeke ('93) in 

 the ovarian egg of Scorpaena scrofa. In none of these species, 

 however, have Keimbahn-determinants been discovered. 



According to Buchner ('10b) the 'besonderer Korper' in the 

 egg of Sagitta and, in fact, Keimbahn-determinants in most 

 other animals are of a chromidial nature, representing the tropho- 

 chromatin demanded by the binuclearity hypothesis. The 

 term chromidia was introduced by R. Hertwig in 1902 and 

 applied to certain chromatin strands and granules of nuclear 

 origin in the cytoplasm of Actinosphaerium. Goldschmidt 

 ('04) transferred the chromidia hypothesis to the tissue cells 

 of Ascaris. Since then chromidia have been described in the 

 cells of many animals, including both somatic and germ cells. 

 Thus far the group of zoologists which favor the chromidia idea 

 has not received very extensive backing, but the fact remains 



