io8 THE LEECHES OE MINNESOTA 



customary disposition. The latter can be very favorably studied on 

 the dorsal surface but are difficult to distinguish on the generally light 

 background of the ventral surface. 



Somites I, II and III are uniannulate, IV and V biannulate, and 

 VI triannulate on the dorsal side. Somites VII and VIII arc re- 

 spectively triannulate and quadriannulate but VII oj and VIII ai are 

 enlarged and quite distinctly subdivided dorsally. Then follow sixteen 

 complete quinquiannulate somites, IX to XXIV inclusive, in which 

 the neural annulus is typically shorter than any of the others. At 

 the posterior end XXV is again quadriannulate, there being only one 

 post-neural annulus (aj) instead of two, XXVI is biannulate with ai 

 more or less distinctly separated from 02. The large anus cuts into 

 the posterior margin of XXVII. 



As in all of the predatory leeches of this family the mouth is of 

 large size and may be considered to be coextensive with the opening 

 of the oral sucker. The three jaws exhibit the usual relations, but 

 their form is characteristic of the species among the leeches of the 

 northern United States. They are about twice as long as high and 

 each bears about sixty-five fine conical, slightly retrorse. uniserial 

 teeth. A very short pharynx with several longitudinal folds reaches 

 to about IX, within which segment it is succeeded by a still shorter 

 oesophagus which can scarcely be distinguished from the stomach, as 

 sacculations begin to be evident immediately. From X to XVIII in- 

 clusive each somite includes two pairs of gastric caeca of which those 

 from XIII backward are of large size. The last pair, which originate 

 from the stomach in the anterior part of somite XIX, are of very great 

 extent, reaching XXIV or XXV, and bear two wide lateral branches 

 in each of the intervening somites. The straight narrow intestine pre- 

 sents no noteworthy features. 



Ten pairs of testes are situated, intermetamerically, as most usual 

 in the leeches, at XIII/XIV to XXII/XXIII inclusive. The vasa 

 deferentia are enveloped in crowded unicellular glands and follow 

 somewhat sinuous courses. In somite XI they lose their glandular 

 covering and appear as delicate ducts, which opposite to ganglion XI 

 pass abruptly into the anterior end of the compact massive epididymes. 

 From the posterior end of the latter wide somewhat folded ducti 

 ejaculatorii lead to the terminal organ. Just before entering the outer 

 glandular covering of the bursa or atrium the ducti become constricted 

 and then rise as a pair of slightly enlarged sacs which open into the 

 summit of the invaginated bursa to which they stand in the relation 



