STUDIES ON GERM CELLS 429 



aus Mesodermzellen, die in die Mesodermrohren von der Bauch- 

 seite herindringen." Doubt was immediately cast on these 

 results, although Weismann ('04) vouched for their accuracy. 

 Thus Wheeler ('04) says: 



Even in his first paper there is no satisfactory evidence to show that 

 the cells regarded as derivatives of the polar bodies in the figures on 

 plate 4 are really such, and not dividing cleavage cells or possibly 

 vitellophags .... When we take up the second paper we wonder 

 how anybody could regard the figures there presented as even an adum- 

 bration of proof that the testes of the drone are developed from the 

 polar bodies. 



Dickel ('04) could find no connection between the polar bodies 

 and the cells Petrunkewitsch claims originate from the 'Richtungs- 

 kopulationskern,' but considers these 'Dotterzellen.' Nachts- 

 heim ('13) agrees with Dickel. "Die im Blastodermstadium 

 am Blastoporus liegenden Syncytien sind Dotterzellen, stehen 

 also zu den Richtungskorpern in keiner Beziehung. Sie finden 

 sich in den befruchteten und unbefruchteten Eiern in gleicher 

 Weise, nicht, wie Petrunkewitsch angegeben hat, nur in den 

 letzteren" (p. 198). 



The investigations of Silvestri ('06, '08) on parasitic Hymen- 

 optera are of particular interest, since in both the polyembryonic 

 species and those whose eggs produce a single individual, the 

 keimbahn-determinant is a plasmosome which escapes from the 

 germinal vesicle. Silvestri ('06) first studied Copidosoma (Lito- 

 mastix) truncatellus, a polyembryonic species which lays its eggs 

 in the eggs of the moths of the genus Plusia. In the germinal 

 vesicle of this species are two nucleoli, one chromatic the other 

 plasmatic (fig. 13, A). Just before maturation the plasmosome 

 escapes and becomes situated near the posterior end. Matura- 

 tion occurs near the anterior pole (fig. 13, B). First and second 

 polar bodies are formed, and the first divides, thus making three 

 in all (fig. 13, C); these remain near the anterior end, whereas 

 the female nucleus comes to lie near the nucleolus at the oppo- 

 site pole (fig. 13, C). In both fertilized and parthenogenetic 

 eggs the maturation processes, the behavior of the nucleolus, 

 and segmentation are similar. The nucleolus is segregated in. 



