REPRODUCTIVE ORGANS OF DIOPATRA. 



E. A. ANDREWS. 



In dissecting a large species of the annelid Diopatra at Beau- 

 fort, North Carolina, in June, 1888, my attention was attracted 

 by certain peculiar strings of green cells occurring abundantly 

 in the body cavity, From the chlorophyll-like appearance of 

 the pigment, the definite cell walls and linear arrangement of 

 the cells in these strings, as well as from the marked shrinkage 

 of the protoplasm, after the manner of a primordial utricle, these 

 objects were at first mistaken for parasitic algae. Examination, 

 however, soon showed that the cell strings were connected with 

 ova both free in the body cavity and when in the ovary, and 

 that they were in fact merely ovarian cells liberated along with 

 the ova, and remaining for a time attached to them as peculiar 

 processes. Such cell strings were found not only in the above 

 species, described below as Diopatra magna, but also in D. cnprea, 

 Bosc, which is less abundant at Beaufort. Moreover, the same 

 cell strings were found and studied in this latter species at 

 Wood's Holl, Massachusetts, later in the same summer. 



As these cell strings and their connection with the ova pre- 

 sent some unique aspects of the history of ovarian cells, a detailed 

 account of them may not be without interest. The general 

 appearance of one of these cell strings is shown in Fig. 1, where 

 the spherical ovum is seen to be provided with two nearly equal 

 tails or strings of cells, larger where attached to the ovum, and 

 diminishing towards the free tip. Each cell, and the ovum also, 

 has its nucleus, and, at this stage, its nucleolus, while bright 

 green pigment is especially noticeable in the ovum. This 

 pigment varies in amount, some cases observed at Beaufort, 

 in D. magna particularly, showing the green color much more 

 conspicuously than the majority of those seen at Wood's Holl. 



Floating about freely in the body cavity, these strings increase 

 in diameter and in length, while the ovum grows still more 

 markedly. Various stages of this gradual growth are repre- 

 sented in Fig. 2 : here it will be noticed that the branching of 



