122 THE LEECHES OF MINNESOTA 



The testes are numerous, about fifty to sixty on each side of 

 somites XVIII to XXIV, mostly with separate vasa efferentia. The 

 enlarged and much convoluted epididymis or sperm sac reaches from 

 XVIII to XIV. There is a long pre-atrial loop to the ejaculatory 

 duct reaching to ganglion XI. The atrium consists of a small eversible 

 bursa and a pair of elongated semi-erect, curved prostate cornua, the 

 bases of which are enveloped by a thick layer of prostate glands. The 

 ovaries are elongated sacs each doubled on itself and reaching for 

 a variable distance through the ventral sinus. 



In this species the color varies extremely. Young individuals us- 

 ually contain little or no pigment, permitting the red color of the blood 

 to appear through the translucent tissues. The adult pigmentation is 

 assumed gradually with increase in age and size. When full grown 

 the ground color may be plumbeous, slate color, brownish gray, olive 

 brown, fuscous, light brown or chocolate, always somewhat lighter 

 ventrally and in the furrows and enlivened on the margins by the red 

 tint of the lateral blood vessel. Sometimes a beautiful golden green 

 hue overspreads the entire dorsum. The browns are most usual and 

 may be plain or more usually more or less marked with irregular black 

 spots with light centers, arranged in two or four longitudinal lines 

 leaving the middle of the back and the margins clear. 



Habits — Within the area of its distribution, which is extensive, 

 this leech occurs under a great variety of conditions. Almost every 

 spring, brook and river, ditch, pond and lake, no matter how pure and 

 cold or how warm and foul, is its home. And in most situations it 

 is by far the most common species of leech present, exceeding in num- 

 bers even the omnipresent Glossiphonia st a gnu! is. The size varies 

 greatly with the extent of the body of water and the richness of the 

 food supply. Small clear brooks and ditches almost invariably yield 

 only small individuals, while by far the largest individuals which I 

 have seen come from large rivers and ponds and the Great Lakes. 

 Bristol has pointed out that in any particular pond they congregate 

 on the shore which receives the richest food supply and my own ex- 

 perience substantiates this. 



Like many other species of leeches this one conceals itself during 

 the day beneath stones, logs, leaves or whatever happens to be con- 

 venient for the purpose, but leaves its shelter at night and searches 

 actively for food. In aquaria the rhythmic respiratory movement, 

 which, takes place while cither both or only the posterior sucker is at- 

 tached, may be frequently observed. It is so muscular and the body so 



