120 ANDREWS. [Vol. V. 



If the suspension of the ovum at an early stage by means of 

 cell strings has any direct utility, I would incline to seek it in 

 the advantage derived from a greater free access to the body- 

 cavity nutriment thus attained, and regard the cell strings as 

 chiefly, if not entirely, mechanical supports subsequently re- 

 tained for a while as, possibly, furnishing some advantages by 

 keeping the ova separate and well surrounded by the nutrient 

 liquid while floating about. They are eventually lost when the 

 ovum approaches maturity and prepares to pass out of the body 

 cavity into the nephridial tubes. 



Perhaps, however, the whole arrangement is only the neces- 

 sary result of unknown laws of growth of the ovarian cells, and 

 results in no advantage at all comparable to the peculiarity of 

 the structure produced. 



Whatever may prove to be the function of these cell strings, 

 if any, their occurrence seems to be confined to Diopatra, as far 

 as I know. The nearest approach to this condition of things is 

 seen, perhaps, in Bonellia, where also the ovum is armed with a 

 collection of cells adhering to its periphery at one point, and of 

 no apparent use. These cells form, to be sure, a spherical mass, 

 but agree with the cell strings of Diopatra in having the same 

 origin as the ovum, which in both cases is differentiated by 

 growth beyond the condition attained by the majority of the 

 ovarian cells. Sections of the cell mass given by Spengel show 

 a striking resemblance to the connection of ovum and cell string 

 in Diopatra. Moreover, the resulting cell mass remains upon 

 the pole of the ovum remote from the eccentric nucleus, and 

 this, I am inclined to think, is the case with the cell strings in 

 Diopatra. The relative position of the auxiliary cells with ref- 

 erence to the ovum and ovary is, however, opposite in the two 

 cases, and it does not appear that even a suspensory function 

 could be ascribed to them in Bonellia. 



Baltimore, Dec. 8. 1890. 



As the large Diopatra upon which the above observations 

 were first made does not occur upon our Northern coast, and as 

 it is as yet undescribed, a brief description of it, with illustra- 

 tions of some of its characters, may be here appended, indicat- 

 ing its considerable departure from the common D. cuprea. 



