192 ISAO IIJIMA. 



Their number is not limited to one pair in each segment, as 

 in most leeches. I once counted as many as sixty-two on 

 one side of the median line." It is impossible to say pre- 

 cisely how many occur in each segment ; but as they extend 

 through about six segments, the average number cannot be 

 far from twenty on one side of the median line. 



From what I could learn from my sections and dissections, 

 I am inclined to think that the testicular sacs are sessile and 

 not connected to the vasa deferentia by special stalk -like 

 ducts, as in Hirudo and some other leeches. 



The seminal ducts, or vasa deferentia, in this part of the 

 body are minute tubes, which pass along the under side of 

 the testicular sacs {vd.., fig. 1). Just in front of the fore- 

 most testis each seminal duct abruptly enlarges to a diameter 

 of about "7 mm., and at the same time assumes the form of 

 an elongated coil, which reaches forward to the hind end of 

 the ovaries. It is in this portion {vd.^, fig. 1) that one 

 always finds, especially in the latter part of winter, before 

 copulation has taken place, numerous bundles of sperma- 

 tozoa ; and it is this portion which can be seen through the 

 body-wall cf the living specimen, as a white convoluted 

 streak. 



From near the posterior end of the coiled portion the dia- 

 meter of the seminal duct gradually diminishes as it passes 

 forward, reaching its minimum near vd.^^ {'12 mm). At the 

 level of the fifth ganglion (counting the one immediately 

 behind the suboesophageal ganglion as the first) the seminal 

 duct makes a bend and passes back into one of the horns of 

 the ejaculatory organ ("la bourse," Moquin-Tandon ; " zwei- 

 horniger kurzer Sack," Leuckart). 



It will be necessary to give here a brief description of this 

 organ, in order to render intelligible what I shall have to 

 say concerning copulation. It consists of a main median 

 portion and two lateral horns, the form and position of 

 which may be seen from fig. 1. The lumen of the median 

 portion passes directly into that of each horn, so that the 

 cavity of the organ corresponds nearly with its external 

 form. The wall may be briefly described as consisting 

 of an outer thick muscular layer and an inner lining epithe- 

 lium of a glandular character. 



The ejaculatory organ is supplied with a mass of unicel- 

 lular glands, arranged belt-like around it, just below the 

 junction of the horns. This glandular mass is analogous to 

 that which is found in otlier leeches occupying a similar 

 position, and, according to Leuckart (No. 4, p. 675, vol. i), 

 it may be regarded as a sort of Prostata, whose granular 



