ON A NEW HISTRIOBDELLID. 321 



glands. The irregular masses which he figures as projecting 

 into the cavities of the vesicles^ and which he describes as 

 '' des corps allonges, plus ou moins cylindriques, droits ou 

 non, homogenes, tres ref ringents sur le vivant et qui semblent 

 unis aux parois par une base assez larges/'^ are probably 

 the masses of the accumulated secretion of these glands to 

 which reference is made above. 



In the female the ovaries (figs. 11 and 12; ov., fig. 17) 

 occupy a corresponding position in the body to that occupied 

 by the testes in the male. Anteriorly they diverge ; poste- 

 riorly they are coalescent. The formation of the ova begins 

 in the anterior portion of each ovary (fig. 11), and as we 

 pass backwards they advance in development. In nearly all 

 the specimens examined the whole of the posterior part of 

 the united ovaries is composed of a single immense ovum, 

 very much larger than any of the rest, and occupying nearly 

 the entire interior of the body in this situation, the alimen- 

 tary canal and also the nerve-cord being in this position 

 greatly attenuated. The diameter of this relatively enormous 

 ovum is as much as "2 mm.; its nucleus about -02 mm. Its 

 cytoplasm is coarsely granular, in which it contrasts strongly 

 with that of the smaller ova. In a few cases, however, there 

 is a second ovum, somewhat approaching the largest in size, 

 and resembling it in the coarsely granular character of the 

 cytoplasm. 



The entire ovary is invested in a layer of nucleated mate- 

 rial, which is probably to be regarded as specially developed 

 peritoneal epithelium. Probably it is from the cells of this 

 layer that new ova are formed. It foi'ms a complete investment 

 for all the larger ova, and this investing follicle, which is of 

 considerable thickness in an ovum approaching maturity, 

 has doubtless the function of ministering to its nourishment. 



A pair of specially modified nephridia appear to act as 

 oviducts (fig. 11, od.). These open on the exterior in a 

 lateral position behind the second pair of cirri, and opposite 

 the anterior paired portions of the ovary. Each runs first 



^ L. c, p. 487. 



