CHROMOSOMES AND MITOCIIOXDRIA ^71 



somes (shown in black in Fig. 74), two lar^e sex- 

 chromosomes (dotted), and two small sex-clironio- 



Spermato- 

 gonium 



Spermato- 

 cyte 1. Ordn. 



Spermato- 

 cyte 2. Ordn 



Spermien 



Oogonium. 



/^^p^\\ Oocyte 1. Ordn. 



C /• J Oocyte 2. Ordn. 



Reifes Ei. 



Fig. 74. — Diagrams showing the chromosome cycle in the pteropod 

 mollusk, Creseis acicula. In order to sinipHfy thi- (Ha^rams each 

 black chromosome is made to represent ei^ht ordinary chromosomes. 

 {After Zarnik, 1911.) 



somes (dotted). The spermalo^'oiiia outer the mat- 

 uration period in this condition. The nuniljcr of 



