No. 501] 



NOTES AND LITER A TURK 



the end of such a tip opens and a sperm nucleus enters the egg, 

 passing quickly to the female nucleus, which lies in the center 

 and is without an evident central body. The sperm nucleus 

 increases in size until the two fusing gamete nuclei become indis- 

 tinguishable. The mitoses of oospore germination were not 

 observed. Claussen found no bi- and tri-nucleate eggs in Sapro- 

 legnia monoica as were reported by Davis for an apandrous 

 form of Saprolegnia mixta. 



Studies on several species of Vaucheria by Heidinger 2 are 

 reported in a lengthy paper by Heidinger on the development 

 of their sexual organs. The investigation was conducted in the 

 laboratory of Oltmanns and centers around the disputed point 

 as to how the mature oogonium with its one egg comes to contain 

 a single nucleus, when the young oogonium is multinucleate. 

 Oltmanns described the migration or withdrawal into the main 

 filament of all of the numerous nuclei present in the young 

 oogonium with the exception of one, which remained to become 

 the nucleus of the egg. Davis holds that the young oogonium 

 is multinucleate even after the formation of the cross wall, 

 separating it from the parent filament, and that there is a process 

 of nuclear degeneration during which all break down with the 

 exception of a single surviving nucleus that comes to lie in the 

 center of the egg. 



ITcid inker's conclusions are in agreement with the views of 

 Oltmanns. All of the numerous nuclei except the future egg 

 nucleus are said to leave the developing oogonium and to pass 

 back into the parent filament before the appearance of the cross 

 wall which separates the oogonium from the parent filament. 

 Heidinger finds no process of nuclear defeneration as described 

 by Davis. The egg nucleus, which remains after the process of 

 nuclear migration, lies at first at the tip of the oogonium and is 

 accompanied by a centrosome-like body, with protoplasmic radia- 

 tions, similar to the central body described by Claussen for the 

 eggs of Saprolegnia: shortly before fertilization this nucleus 

 passes to the center of the egg. 



The paper gives many details of the series of events during 

 the period of fructification and describes interesting culture 

 methods. The cytologies! account is, however, open to criticism. 

 The fixation was in V2-I per cent, chrom-acetic acid, a very 



