SEXUAL ORGANS AND THEIR PRODUCTS IN PHORONIS. 



153 



in preparation for the second division. /, one of the four sper- 

 matids formed from a spermatocyte, with spherical nucleus, g, 

 h, i, spermatids with dense, narrow and bent nucleus in different 

 stages of growth into spermatozoan head. /, ripe spermatozoa. 

 (Zeiss, oc 12 and obj. 1.5 mm. apochr. syst.). 



