No. 2.] ANATOA/V OF BDELLODRILUS ILLUMINATUS. 525 



around which the ova frequently wrap, serve the same purpose. 

 Large coarsely granular masses, which Voigt regards as fatty 

 degenerated ova, are frequently present, and appear to be 

 absorbed by the maturing ova. 



No free oviducts are present, the mature ova escaping by a 

 pair of simple ovipores (Fig. 28), which are ridiculously small 

 as compared to the mature ova, though capable of considerable 

 distention, and perforate the body walls in the constriction 

 between the major and minor annuli of the seventh somite, 

 each in the ventral octant of its respective side. The lining 

 epithelium resembles that of the copulatory bursa, etc., and 

 spreads out on all sides of the internal aperture as a flaring 

 lip (Fig. 28). Cilia are wanting, and the ova are extruded by 

 pressure of the body muscles, a process which may be success- 

 fully simulated by artificial means. The ova are very plastic, but 

 at once assume a rounded form in the water. Fig. 28 is taken 

 from a preparation of B. philadelphicus, as the section passed 

 through a more favorable plane for representation than any of 

 B. illuminatus. No essential difference, however, is observ- 

 able between the two species. Note, however, the much 

 larger size of the longitudinal muscle fibres and the smaller 

 size of the epidermal nuclei in B. philadelphicus. Part of 

 an ovum is shown at a lying opposite to the mouth of the 

 ovipore. 



As in Branchiobdella, the spermatheca is unpaired ; but in 

 the present species has a very characteristic form (Figs, i 

 and 29). The proximal portion opening on the ventral surface 

 of the fifth somite is sub-cylindrical, but expanded just within 

 the mouth by large anterior and posterior glands. Dorsally 

 by the side of the intestine it splits into a pair of clavate 

 sacs, of which the external (Fig. 29, 0) is the larger, and is 

 often thrown into a coil. The internal slightly smaller sac (/) 

 has usually the appearance of a lateral branch, being more dis- 

 placed from the axis of the organ than the outer. The lining 

 epithelium has also a more glandular appearance (Fig. 30). In 

 living animals both divisions show slight terminal enlargements, 

 and, owing to contractions of the muscular coat, irregularities 

 in diameter. 



