THE LEECHES OF MINNESOTA in 



latter is more fully elaborated dorsally. On the typically biannulate 

 somite VI, ai and a2 are more or less separated by a furrow confined 

 to more or less of the middle dorsal region. Somite VII is fully 

 triannulate but is peculiar in the large size of aj, which, moreover, may 

 exhibit a faint dividing furrow ; VIII is quadriannulate and ai re- 

 sembles VII flj in being enlarged and partly subdivided. There are 

 fifteen (IX to XXIII) quinquiannulate somites, in which all of the 

 annuli are approximately equal. Somite XXIV is quadriannulate and 

 sometimes the last annulus (aj) is faintly subdivided, usually on the 

 ventral surface ; XXV is triannulate, but ai, which is normally of 

 larger size than the remaining annuli, js subject to much variation. 

 The following two somites, XXVI and XXVII, are variable and 

 difficult to interpret, but the uniannulate condition is probably the 

 most usual. 



Just anterior to the jaws and separating them from the buccal 

 area is a slight circular sulcus and fold. The jaws are low and 

 rounded, not at all compressed on the free edge. As usual they may 

 be retracted into little pockets so that the entire toothbearing surface 

 is concealed. Each jaw bears a double file of large, coarse teeth ar- 

 ranged in from twelve to sixteen pairs. The pharynx reaches to X and 

 has from nine to twelve or more longitudinal folds, three of which 

 unite into a strong ridge behind each jaw. The long narrow stomach 

 leaches to XIX, and is provided along its entire length with numerous 

 small pockets ; at its posterior end a pair of large caeca arise and reach 

 caudad to XXII or XXIII. The intestine is also straight and bears 

 two or three pairs of quite large, short, globular caeca which lie dorsad 

 of the large posterior gastric caeca. The anus is very large. 



The customary ten pairs of testes are present in the anterior 

 end of somites XIV to XXIII each reaching into the preceding somite. 

 The collecting portion of the vasa efferenta and vas deferens are es- 

 sentially similar to those of Macrobdclla. The epididymis is a rather 

 narrow tube, much convoluted, rather open and not at all massive. 

 The epididymis opens into the small fusiform sperm sac in the 

 posterior part of XIII and the latter is continued as the ductus ejacu- 

 latorius. This canal reaches forward to the level of the male pore 

 and then bends back to join the closed end of the atrium, sometimes 

 the right, sometimes the left one, passing beneath the nerve cord. The 

 atrium or penis sheath is very long and slender, with a sharp bend 

 at ganglion XVII, from which point one limb reaches to the male 

 pore, the other to the anterior end of somite XV ; the ratio of the 



