No. i.] REPRODUCTIVE ORGANS OF DIOPATRA. 1 19 



clusters were found separating or dividing into halves, in each 

 of which the nuclei became much smaller and apparently homo- 

 geneous (c). These smallest, ultimate nuclei lose their cohesion, 

 and separating, float freely in body-cavity liquid, where each 

 becomes converted into a mature spermatozoon, having the gen- 

 eral form shown in Fig. 9, m. Crescent-shaped intermediate 

 forms often float about, marked on one side by a conspicuous, 

 deeply stained, drop-like body. 



In D. cuprea the general development of the spermatozoa is 

 the same as in the above description of D. magna, yet the form 

 of the perfect spermatozoon is strikingly different (Fig. 9, c), 

 considering that we have here two species of the same genus, 

 furnishing a case of dimorphism similar to that of certain spe- 

 cies of the common frog, Rana. 



The most noticeable feature in the formation of the reproduc- 

 tive cells in these Annelids lies in the fact that the ova of the 

 female are accompanied during a considerable part of their 

 growth, while free in the body-cavity liquid, by a collection of 

 ovarian cells, cell strings, having no apparent function, though 

 at first identical with the ovum itself. 



The survival of one ovarian cell at the expense of others is 

 common, and the linear arrangement of such sets of cells in the 

 ovary is not unknown ; but I know of no case in which such 

 sister cells of the. ova remain so long as peculiar appendages to 

 the ovum. In this case there seems no ground for assuming 

 that the ova derive nourishment directly from the ovarian cells, 

 or at least from the separated ones of the cell strings ; the early 

 presence of a firm egg membrane precluding any ingestion of 

 entire cells, while the radial pores in the membrane, even if they 

 are present at an early period, are too small to take in yolk 

 bodies as solids, much less entire cells. Of course it cannot be 

 denied that pseudopodia-like processes, or continuity of proto- 

 plasm, may exist between ovum and cell strings, but the small 

 area of the ovum occupied by the attachment of these strings 

 would seem to be insufficient to account for the large increase 

 of bulk taking place in the ovum. That the cell strings play 

 but little if any part in the supply of nourishment to the ovum 

 is also indicated by their insignificance when the yolk spherules 

 appear, and by their entire absence during the later stage of 

 growth of the ovum. 



