Boyal Microscopical Socieiy. Ill 



The single species of Annelid, that I have been able to examine, 

 Aphrodite sj). ? has zoosperms very much like those of A. crenaster, 

 but smaller, presenting a globular body, with a slight tendency in 

 some cases towards a pointed oval shape. The centre is occupied 

 by a brighter spot (Fig. 13). The caput measured about " 002 mm. 

 The tail, which, like that of the Holothuria, is of extreme tenuity, 

 measures about thirteen to fifteen times the diameter of the head. 

 The motions of these zoosperms are not so lively as those of the 

 latter species. Sea- water also acts more slowly on them, but after 

 a time they expand and become mere transparent vesicles when 

 placed in that fluid, but there is no appearance of the refractive 

 particle adhering to the circumference. The zoosperms in this 

 animal differ less apparently from those of the starfish, which 

 belongs to another class, than do the zoosperms of one species 

 of crustacean from those of another and nearly allied species ; and 

 indeed it is curious to note the varieties in the shape of these 

 bodies, and it would be interesting to find out the cause. The 

 Ostracoda for instance, as described by Dr. Zenker,* have most 

 enormous zoosperms having the appearance of a twisted rope, but 

 creating the impression in one's mind that they must be spermato- 

 phora. 



The subject ofiers a wide field for research for those in want 

 of an occupation for their microscopes of more physiological interest 

 than perhaps even the markings of diatoms ; and although much 

 has been done by men like Kolliker in the general subject, and 

 incidentally to their special studies by Claparede and Quatrefages, 

 yet more remains for future explorers. 



* Wiegmaii's ' Archiv f. Natur Geschichte,' 1854, Jahrg. xx. 



