MECHANISM IN SEGREGATION 



47 



the ordinary mitotic process. The cells then pass into the 

 synaptic stage (Fig. 20, a-d). As the chromosomes begin 



Fia. 19. — Thin-thread stage of Tomopteris spermatocyte, a-d; tetrads, e; first sperma- 

 tocyte division, /-?; second spermatocyte division, j-Z. (After Schreiner). 



to emerge as thin threads, it is found in Batracoseps that 

 their ends are all pointed towards one pole (Fig. 20, dZ). 

 This is the same pole as that towards which the two ends 



