Leeches 21 



latter part of the nineteenth segment, are of very great extent, reach- 

 ing backward into segment twenty- four or twenty-five and bearing 

 two wide lateral branches in each of the intervening segments. The 

 straight narrow intestine presents no noteworthy features. 



While presenting the general features characteristic of the family 

 the reproductive organs (figure 12 B, and 12 C) are in many details 

 peculiar. There are ten pairs of testes situated at the boundaries 

 between contiguous segments from the thirteenth and fourteenth to 

 the twenty-second and twenty-third inclusive. Their delicate ducts, 

 all of which unite in a pair of longitudinal canals, the vasa deferentia, 

 are like the latter covered with minute unicellular glands and follow a 

 somewhat winding course. The glandular coat ceases at the eleventh 

 segment where the vasa appear as smooth very delicate tubes, and at 

 the level of the ganglion of that segment pass abruptly into the pair 

 of massive compact epididymes. From its posterior end each of the 

 latter is continued as a rather wide somewhat folded ejectory duct 

 leading to the single median terminal or copulatory organ. Just 

 before entering the outer or glandular layer of the so-called penial 

 bursa, or atrium, the ducts become constricted and then rise as a 

 pair of slightly enlarged sacs which open into the summits of the 

 large inner end of the bursa, to which they stand in the relation of a 

 pair of horns. This median bursa which evaginates to form the penis 

 is in its retracted condition spherical or inverted pyriform in shape, 

 and its thick walls consist of mucous, muscular and glandular coats. 

 Within it the spermatophores or bundles of spermatozoa which are 

 transferred during copulation, are formed. 



During life the colors are very rich and showy. On the upper 

 surface the ground varies from a light sage-green to a dark olive- 

 green with obscure dark longitudinal lines or streaks in the median 

 area. Down the median line is a series (sometimes absent) of small 

 but very conspicuous cadmium-orange or light red spots, one to 

 each segment. On each side close to the margins is a similarly 

 arranged series of small black spots. The lower surface is of rich 

 orange varying in shade and intensity, sometimes plain, sometimes 

 spotted to a varying degree with black. 



Distribution, Habits and Ecological Relations. The American 

 medicinal leech is widely distributed throughout the northern United 

 States and southern Canada. It extends across the entire width of 

 the continent and has been taken in every state from Maine to 

 Washington. The known north and south range is from Labrador 

 to Kansas and Virginia. In the southern United States it is reolaced 

 by other blood-sucking leeches of the genera Macrobdella, Philob- 

 dclla and Limnatis. 



In the Palisades Interstate Park this leech is more plentiful in Carr 

 Pond than elsewhere, though it occurs in smaller numbers in some 

 of the other lakes but not sufficiently to be considered a pest by 

 bathers. Even in Carr Pond it is not nearly so abundant as in many 

 ponds in eastern Pennsylvania and Massachusetts, or in the lakes of 

 Wisconsin and Minnesota. Observations made at the swimming 



