THE LEECHES OF JAPAN. 363 
Gratiolet finds one hundred and two annuliin H. medi- 
cinalis, as will be seen from the following figures : 
From tip of head to first pair of nephridial pores . é ‘ 10 
Between first and last pair of nephridial pores .. Md cee 4 
Between last pair of pores andanus_ . ; : : ' 9 
Acetabulum ‘ i : : : : ; d 6 
Total number . ; ‘ , . 102 
Following the same order in the case of H. nipponia 
omitting the acetabulum, we have : 
From tip of head to first pair of pores. 2 ; : : 13 
Between first and last pair of pores. : : ‘ : 80 
Between last pair of pores and anus . : : ; : 8 
Between anus and acetabulum. : : : i! 
Total number . ; : ; . 102 
The most important difference here is found in the number 
of rings that separate the two extreme pairs of nephridial 
pores. In the Japanese Leech (fig. 10), there are sixteen 
unabridged somites between these two points, the 7th to 
the 22nd inclusive. In the European Leech, according to the 
statements cited from Gratiolet, the 7th somite is composed 
of three rings, and the 8th of four rings; the remaining 
fourteen containing each five rings. Thus, if we accept 
Gratiolet’s statements, we must allow that H. medicinalis 
has eight abbreviated somites at the anterior end, 
while H. nipponia has only six abbreviated at this end. 
Now such a difference is, as will be shown in the sequel, quite 
irreconcilable with the opinion that the two species belong 
to the same genus. In order to remove all doubts as to the 
propriety of placing the Japanese Leech in the genus Hirudo, 
I have examined a considerable number of Medicinal Leeches 
from different parts of Europe and Asia, as well as Aulostoma, 
Hemopis, and Macrobdella Verrill. This examination has 
brought to light some facts concerning the composition of the 
body of the Leech, which has hitherto escaped notice, facts 
which will serve as a basis for comparative systematic studies, 
