24 Roosevelt Wild Life Bulletin 



grammes. In correspondence with the extreme slowness and com- 

 pleteness of digestion the intestine is short and simple and the anus 

 is minute. 



As indicated, the food is typically vertebrate blood derived from 

 men or cattle entering the water, or in their absence from frogs 

 (figure 13, B), tadpoles, fishes or turtles. Frogs' eggs, (figure 13, C) 

 aquatic worms (Tubificidae), and occasionally insect larvae are also 

 eaten. In attacking fishes, favorite points are the gills and isthmus, 

 both highly vascular regions. In the case of frogs the leech will 

 sometimes perforate the skin and insert the cephalic end into the 

 subcutaneous lymph spaces, in which case the large blood vessels 

 may be reached and death result very quickly. 



These leeches are extremely sensitive to the presence of food. If, 

 in a vessel containing several, a finger be touched lightly on the 

 bottom, after a short interval the leeches become restless and begin 

 exploratory movements in the course of which the head is passed 

 over the spot touched and immediately arrested, upon w^hich increased 

 excitation follows with more minute and long continued exploration 

 of this spot. It is quite evident from their actions that they detect 

 the presence of the emanations left by the finger. A little blood 

 escaping from a cut is an even greater and farther reaching attraction, 

 and the leeches will gather from considerable distances to the 

 promised feast. This habit may be taken advantage of in collecting 

 the leeches and has been used effectively by the writer in the vicinity 

 of Philadelphia. Movements of the water and the disturbance of the 

 bottom such as results from men or cattle wading or swimming also 

 attract the leeches even when animal odors are eliminated, as is 

 shown by wading in rubber boots or by the use of a pole. After such 

 disturbances tlie leeches may be seen leaving their places of conceal- 

 ment and crawling or swimming in search of the expected prey, if 

 one may so express the reaction in terms of the consciousness that 

 the animals lack. 



Ordinarily Macrobdella is negatively phototropic, remaining con- 

 cealed in dark places during the day and becoming active at night 

 when presumably frogs and fishes are naturally preyed upon; but if 

 hungry the impulse aroused by the stimuli indicating the presence of 

 food overcomes the impulse toward concealment and they will swim 

 freely during daylight. Otherwise this study would not have had its 

 inception. When well fed they remain quiescent and relaxed under 

 stones and logs near the water's edge, assuming a variety of resting 

 attitudes often partly out of the water. This latter habit is well 

 illustrated when they are kept in the laboratory in aquaria, in which 

 case a favorite position is with one or both suckers attached to the 

 glass above the water's edge, the body being permitted to hang laxly 

 more or less into the water. 



Under such circumstances the supply of oxygen is abundant and 

 no respiratory movements take place, but when immersed in water 

 in which the oxygen supply is deficient they exhibit rhythmic undu- 

 latory movements that may be quickened or retarded by other stimuli, 

 such as arise from light changes or contacts. This movement varies 



