28 Roosevelt Wild Life Bulletin 



latter by a Centigrade chemical thermometer encased in a brass tube. 

 All of the experiments on both dormant and active leeches fixed the 

 lethal temperature at about 20 "^F. When thawed out slowly and 

 carefully after such freezing the leeches were always found to be 

 completely dead, A'ery much relaxed, somewhat swollen, soft and 

 flaccid, very different from the more or less rigid, turgid state of 

 these leeches when killed by strong mineral or narcotic poisons. 



In the spring as the water warms the leeches gradually become 

 active, appearing wnth the frogs upon which and their eggs they 

 largely feed (figure 13, B, C). At this time, and to a less extent later 

 in the summer, and then only when unfed, they are prone to wander. 

 If kept in an aquarium they will frequently crawl over the sides 

 during the night and occasionally even by day and drop to the floor. 

 I have often found them by following the glistening trail of dried 

 mucous wiped free of all dust and meandering about the floor for 

 perhaps as much as one hundred feet. When found the leech will 

 present a shrunken, more or less dried appearance, and will be 

 covered with adhering dust. If too great a time has not elapsed 

 they may be revived by immersion in water even after shrinking to 

 one-third of their former size and weight. The principal loss has 

 been of water in the form of mucus, and absorption of water takes 

 place rapidly, the animals soon regaining their normal size and 

 activities. This peculiarity- is of much value to individuals of the 

 species living in small rain-fed ponds from which the water com- 

 pletely evaporates during dr}- summers. Under such circumstances 

 these leeches bury themselves in mucus-lined mud cells beneath stones 

 and logs, shrink in size and become dormant. How long they will 

 live under such conditions has not been determined, but they have 

 been found unharmed after such a pond has been dry and the bottom 

 mud hard and cracked for three or four weeks. 



When the leeches become active in the spring they are usually 

 voracious and feed eagerly. After being well fed they copulate. In 

 this act the ventral surfaces of two individuals are brought together 

 in the region of the genital pores, the heads being pointed in opposite 

 directions (figure 13, D). The glairy secretion of the copulatory 

 glands aids cohesion, which is further assisted by one or both indi- 

 viduals taking a loop round the other or by attachment of the suckers. 

 The muscles in the genital region contract strongly, often forming a 

 constriction, the penial or copulatory bursa is everted, and the con- 

 tained spermatophore attached within the vagina of the other indi- 

 vidual or at its orifice. The transfer of a spermatophore may be 

 reciprocal or one-way. 



The actual formation of the egg-capsules T figure 14) has not been 

 seen in this species, but during June and July they have been found 

 buried in the mud or turf at the water's edge just above or below the 

 water level. They vary from less than one-half to about three- 

 quarters of an inch in length, probably dependent on the size of the 

 producing leech. In shape they are broadly elliptical and in color 

 a pale straw. The structure resembles that of other leeches of the 

 same family, the walls being composed of a cellular spong}- layer of 



