JAPANESE LAND LEECHES. 291 



can not l)e partly outside, and partly inside the clitellum, the rings 

 mentioned are wholly taken in by it. Hence it follows, that in this 

 species the clitellum embraces one ring more than the others. 



Genital pores. The genital orifices are situated in the X and the XI 

 somite respectively. The position which they occupy in these somites 

 is the same in tlie three species. If we assume each of these somites 

 to be divided into eight rings, as is actually the case with Owhdella 

 octonana, we find the m;de opening always on the fifth ring of the X 

 somite and the female (opening on the last ring of the XI. The num- 

 ber of the rings that separate those bearing the genital orifices is 4, 7, 

 and 10, respectively, bat this diiference results agsdn, as in the case of 

 the clitellum, from the diiference in the number of rings that make a 

 complete somite in these species. If we put the external rings out of 

 consideration, these orifices are found to occupy the corresponding 

 portions of the corresponding somites. This very interesting point 

 in their position can easily be understood by referring to the figures 

 A, B, and C, in PI. XXIX. The unmistakable coincidence among 

 the species in regard to the position of the genital openings, as well 

 as to that of the clitellum, speaks strongly for the near relationship 

 of these three kinds of land-leeches. 



Median region. It is in this region thnt the somites show their 

 external constitution most clearly and without any abbreviation. As 

 has been already stated, the leeches belonging \o the present genus have 

 no segmental papillaä that make the somites externally distinguishable, 

 and we are compelled to refer to the internal anatomy for ascertaining 

 their boundaries. This, however, is not very difiicult in the median 

 reHon, where each of the rinti^s lodo-ino- the gfanoflia comes next to that 

 on which the nephridial pores open. A comparison with other leeches 

 belonging to the sub-order JrJnjncJiohdelhv of Bhmchard, tells us 

 that the furrows between these two sorts of rina's mark the limits of 



