THE CHROMOSOMES 



157 



where some of the ends can be seen to be arranged in 

 pairs. As they unite in pairs these thin threads 

 often have the appearance of twisting tightly around 





J 



Fig. 43. — Spcrinatogcnesis of liatracoscps attciiuatus. a, lat(! telophase 

 of spermatogonia! divisitjii; h, resting stage after tlie last spermatogonia! 

 division ; r, appearance of the spireme; (/ and c, later stage of last (bouquet 

 grele); /, r/, A, twisting of Ic.ptotcnf f hniads around each otlicr (ami)hitcne 

 stage); i, ampliitcMu; stage ((entire cc;!!); j, i)achytcnc. stage (hou(iuet 

 pachj-tene); k, longitudinal splitting of threads (strcpsincnia stage); Z, 

 shortening and thickening of the chromosomes. (After Jansscus.) 



