356 C. O. WHITMAN. 
being generally constricted on the papillate rings (fig. 11) or 
entirely interrupted (figs. 17, 19). 
Only a few examples of this Leech were found in Yezo 
(officially called Hokkaido), and these agreed so perfectly with 
those found about Tokio that I am inclined to believe that 
this island is indebted to the main island for its scanty stock 
of Medicinal Leeches. In one specimen obtained in Hakodaté, 
I noticed that the dark borders of the median stripe broadened 
conspicuously on the middle rings of each somite, which is a 
feature not infrequent in the Leeches of Aomori and Tokio. 
Habitat.—This Leech is very abundant in the ditches and 
slow streams in the low plains of Tokio, and especially so in 
the open sewers of this and other cities of the main island. I 
have occasionally found it in shallow pools in rice fields. 
Habits.—Its habits and mode of life are precisely the same 
as those of the Medicinal Leech of Europe. 
Internal Organization.—The structure and relations of 
the internal organs are almost identical with those in H. medi- 
cinalis. There is the same number of ganglia, testes, ne- 
phridia, and cecal appendages of the alimentary tract, and all 
hold precisely the same relative positions. 
The azygous terminal portions of the reproductive organs 
open beneath the nerve-cords, between the sixth and seventh 
and between the seventh and eight pairs of ganglia, counting 
the sub-cesophageal ganglia as the first. The intromittent 
organ lies on the right, the vagina on the left, of the nerve- 
cord. The ovaries (Pl. XXI, fig. 65) are small pyriform sacs 
of about the same size, and occupying the same position with 
relation to the nerve-cord and the ganglia as the testes. They 
lie nearly in the same vertical transverse plane with the vaginal 
orifice, just in front of the vagina. Asin H. medicinalis,} 
the oviduct leading from the right ovary passes under the 
nerve-cord, uniting with the left oviduct at the level of the 
anterior end of the vagina. The common oviduct (od. c.) 
(oviductus communis) is somewhat tortuous, and its 
anterior half is enveloped by a mass of unicellular glands, the 
1 Rolleston, ‘ Forms of Animal Life,’ p. 221, 
