THE LEECHES OF MINNESOTA 105 



ward. About its middle is a constriction and caudad of this an en- 

 largement bearing another pair of caeca. Smaller caeca may occur 

 between. 



There are but five pairs of testes alternating with the gastric 

 sacculations. Very delicate vasa efferentia start at the dorso-mesial 

 side of the testes and then pass forward and outward among the ventral 

 clitellar glands to the vas deferens, a very delicate tube resting on the 

 ventral body walls. Passing ganglion XIV the vas deferens becomes 

 larger and its course wavy and just in front of ganglion XIII expands 

 into a short, wide sperm sac which is looped caudad and, after a con- 

 striction passes into a ductus ejaculatoruis of half its diameter and 

 twice its length. The latter becomes very narrow as it enters the 

 thick loose layer of unicellular glands which conceal the median ever- 

 sible bursa from view. The male orifice is located at XI/XII. ■ The 

 paired ovaries are large elongated simple sacs which even in their 

 much folded condition reach as far caudad as somite XVI. They 

 open at or about XII (12/(13. 



Verrill describes the colors during life as "translucent greenish, 

 with a pale median dorsal line and with minute black specks arranged 

 in transverse bands ; along each side are eight light spots, alternating 

 with the dark punctate bands." The black specks are branched pig- 

 ment cells which are scattered through the integument with singular 

 regularity. Large individuals become more opaque owing to the 

 great development of clitellar glands. 



Habits— This is our commonest fresh water fish leech. It is com- 

 mon in the ponds and lakes of the northern states and the Mississippi 

 Valley and is especially abundant along the Ohio shore of Lake Erie. 

 It lives upon the exterior of the body of various species of small fishes 

 feeding upon the mucous which covers the surface as well as upon 

 their blood. It appears to be in no way injurious to its hosts. Many 

 examples may also be found living among water plants to the stems 

 of which there is good reason to believe its stalked cocoons are at- 

 tached. 



Family Hirudinidae. 



Leeches mostly of large size, more or less elongated, with thick, 

 little depressed bodies. A well-developed zonary clitellum in most 

 species during the breeding season. Oral sucker forming lips sur- 

 rounding the large mouth ; caudal sucker rather small or well de- 

 veloped, discoid. Complete somites usually of 5, rarely of 3 or 7, an- 



