ii 4 THE LEECHES OE MINNESOTA 



//. mannoratis but the following features are diagnostic: Somite VII 

 is fully quadriannulate and YIII quinquiannulate, owing to the com- 

 plete subdivision of VII a? and VIII ai each into two annuli; as a 

 consequence this species has two more annuli in the anterior region; 

 VI flj and VII ai are always relatively wider and may exhibit an 

 incipient furrow ; on the complete somites the annuli are not equal but 

 bear the following relation: — ff<?< &!=&<?< &5=&<5, except at the 

 posterior encf of the series ; finally XXVI and XXVII are typically 

 biannulate. 



Including the rudimentary denticles at the posterior end each jaw 

 bears from twenty to twenty-five pairs of teeth, of smaller size and 

 more irregular form than in H. mannoratis. In other respects the 

 digestive organs are essentially similar in the two species. 



The sperm sacs and epididymes do not reach beyond ganglion XI 

 anteriorly, or ganglion XII posteriorly ; the latter are massive and 

 compact and partly envelope the sperm sacs to which they are closely 

 moulded. The posterior bend of the atrium is at ganglion XIV and 

 the relative length of the two limbs is as one to one and seven-tenths 

 in three examples measured. Although the genital pores are in the 

 homologous annulus they lie two annuli farther from the mouth than 

 in H. mannoratis. The ovaries are always within somite XII, and 

 the vagina never extends posterior to ganglion XIV. 



Forbes thus describes the colors of living examples of the ter- 

 restrial variety— "sooty drab, varying to plumbeous black, somewhat 

 lighter beneath, uniform in tint and quite without spots or mottlings 

 of any sort. A darker median longitudinal stripe, very conspicuous 

 and well defined, is almost invariably present ; a paler marginal stripe 

 often approaching buff, little less constantly so ; and a ventral sub- 

 marginal stripe of the same color as the median dorsal one likewise 

 quite frequent." The ground color of the aquatic variety is similar, 

 but while the dorsal black stripe is less constant it may be very con- 

 spicuous; more frequently it is faint and obscure, broken into small 

 spots or totally wanting. A few small dark spots are sometimes scat- 

 tered over the dorsum. Sensillae are much more distinct in the aquatic 

 than in the terrestrial variety; indeed Forbes failed to find them in the 

 living specimens of the latter. 



Habits — In habitat, food, movements, resting attitudes etc. the 

 aquatic variety is essentially like //. mannoratis. It is capable of a 

 greater degree of extension and appears to be a more active swimmer 

 than that species. Two examples sent to me bv Prof. Nachrtieb and 



