342 C. O. WHITMAN. 
lying before and behind this region, and thus their morpho- 
logical features neither confirm nor contradict the opinion of 
Ebrard. 
In the Land Leech, however, we do find a strongly marked 
histological difference between the vesicles of the clitellum and 
those of the rest of the body, and this fact fully warrants the 
belief that they are in some way subsidiary to the reproductive 
organs. ‘These three pairs of vesicles open in the 27th, 
32nd, and 37th rings, and are thus clearly inside the region of 
the clitellum, which extends from the 25th to the 39th ring. The 
contents of these vesicles could easily be discharged into the 
cocoon, as suggested by Hbrard; but there is at least a possi- 
bility that they assist in the formation of the cocoon, and still 
another that their secretion aids the copulatory process, thus 
serving an end for which special glands have been provided 
in the case of Macrobdella.! 
Under the head of “current statements as to the nephridia,” 
Bourne, after referring to the opinion of Gratiolet and others 
that the nephridia are secretory, comments as follows :— 
“Gratiolet considers that they also serve to keep the skin 
moist while the animal is out of the water, and correlates the 
greater power the Medicinal Leech has of staying out of water 
compared with that of the Horse Leech with the larger size of 
these organs in the former animals. Leydig has shown, how- 
ever, that unicellular glands open all over the surface of the 
skin, and these would serve to keep it moist, just as in Land 
Planarians, the frog, and other terrestrial animals which possess 
a moist skin. I see no reason tosuppose that the nephridia of 
the Leech have any such mucous function.”? 
Moquin-Tandon and Hbrard have called attention to the 
fact before mentioned, that when the surface of the Leech is 
made uncomfortably dry by means of paper or dust, fluid may 
be seen to gather in small drops corresponding in position with 
the nephridial pores. This experiment I have often repeated 
with both aquatic and Land Leeches, and always with the same 
1 Leidy, ‘Proc. Phil. Acad. Nat. Sci.,’ p. 230. 
2 Loe. cit., p. 285. 
