SUMMER PtiANKTOiSf FROM WEST COAST OF SCOTLAND AND IRISH SEA. 2t 



Fig. 30. Later stage of spermatid. The " centrosome " has appeared, aud the axial filament 



is growing out near its constriction. The cytoplasm below the " centrosome " 



has begun to elongate into the tail. 

 Fig. 31. Ditto. In this later stage the chromatin particles of the nucleus have become so 



minute that their individuality is lost. 

 Fig. 32. A later stage of the above. The nucleus is elongating aud is becoming darker. 



The reduction in size of the " centrosome " is noticeable. 

 Fig. 33. Ditto. 

 Fig. 34. The elongation of nucleus and cytoplasm of tail has transformed the spermatid 



into an unripe spermatozoon. The reduction of the " centrosome " is very 



marked. 

 Fig. 35. Ditto. 

 Fig. 36. Final stage before transformation into the ripe spermatozoon. The darkly stained 



nucleus is forming the head, the " centrosome " the middle piece, and the axial 



filament with its surrounding cytoplasm the tail. The " centrosome " lias become 



considerably smaller than it appeared in fig. 35. 



