288 MR FRANK E. BEDDARD 



The further stages in the development of the ova are as follows : — The central mass of 

 protoplasm is always without a nucleus, but soon comes to be clearly separated from the 

 cells surrounding it ; it assumes a polygonal form, which is illustrated in fig. S7,b,c. The 

 surrounding cells, which form a complete investment for the centre mass, lose their 

 pear-shaped outline, and become angular when they are in contact with the neighbouring 

 cells and with the central mass of protoplasm. The outer surface is rounded and convex. 



The nuclei of the cells are very large and unstained, except for a number of rounded 

 granules, of which one is markedly larger than the rest, and corresponds in all probability 

 to the nucleolus. The protoplasm of the cells is, on the contrary, deeply and uniformly 

 stained. 



One of the cells then (see fig. 37, c) begins to enlarge, and eventually becomes larger (d) 

 than the entire mass of the remaining cells with which it rests in contact. I presume that 

 all of the cells become ova in time, but only one (rarely two) was developed at the 

 same time. I have no facts relating to the further development of the ova, which pro- 

 bably become a good deal larger, and filled with yolk. 



Each sphere of developing germinal cells is covered externally by a few nuclei 

 (n, fig. 37), which form a kind of follicle. 



In the early and middle stages, the resemblance of the sphere to a sperm polyplast 

 is extremely close. In both we have a central mass of non-nucleated protoplasm sur- 

 rounded by a single layer of germinal cells, which become ova or spermatozoa, as the case 

 may be. 



The mode of development of the egg in the Oligochseta is treated of by Vejdovsky 

 [7] in his Monograph, chiefly from his own observations, which are the most important 

 in this subject. The development of the ova in Phreodrilus is in most respects 

 similar to the development of the ova in certain Enchytrseidse, which is briefly referred to 

 by Vejdovsky in the work mentioned, and more fully in his " Monographic der 

 Encliytr widen." The cells of the ovary in certain Enchytrseids are arranged in groups 

 exactly as they are in Phreodrilus, but there is only a single string of these groups 

 of cells instead of a large mass, such as I describe in the present paper. 



The development of the ova in the genus Ilyodrilus appears from the figures of Stolc 

 [5] to be very similar to Phreodrilus. 



§ Oviduct. 



The oviduct, as in the Lumbriculidse and Tubificidse, is very short, and consists of little 

 more than the funnel ; the duct leading to the exterior is very short. The oviduct 

 funnel opens into the Xllth segment, and the external pore lies on the boundary line 

 between this segment and the XHIth. In the only specimen (see fig. 18) which I 

 studied by means of sections, the oviduct was not ciliated, and the funnel also had 

 evidently not arrived at maturity. It is interesting to note that the female organs 

 of this worm are not fully mature at the same time as the male organs ; there appears 

 to be here, as in other hermaphrodite organisms, a dichogamy. 



