FAUNA CANADENSIS. 



495 



Bpecimens, liowever, tlie ventral surface is lighter tlian the dorsal, and 

 exhibits two distinct black lines, also somewhat interrupted, and also 

 placed one on each side of the middle line of the body. Both the 

 dorsal and ventral lines are slightly curved, and approach one another 

 toward the two ends of the body. Just at the commencement of the 

 dorsal lines, on the top of the head, are situated six miaute black 

 ocelli, ai-ranged in three closely approximated pairs one behind the 

 other, the two posterior pairs being the largest and most cojispicuous 

 (Fig. 2, b). 



J 



Fig. 2. — Clepsine patelliformis, Nich. — a. Outline of adult viewed from below, 

 showing the mouth, ventral lines, and acetabulum. b. Anterior extremity, 

 enlarged to show the ocelli, c. Young, much enlarged, to show the sacculated 

 stomach and pedunculate sucker. The straight lines indicate the real sizes of the 

 adult and young. 



The habits of this little leech are very remarkable. The adult 

 leech usually places itself with its ventral surface closely appressed to 

 some foreign body, such as a stone or a dead shell, to which it adheres 

 firmly, like a limpet or small Chiton. It is fi'om this habit that 

 the specific name of 'patellifomiis has been chosen. When forcibly 

 detached or irritated, it rolls up like a hedgehog or like the Myriapods 

 of the genus Glomeris. The object served by these peculiar habits 

 becomes obvious when it is seen that almost every individual carries 

 attached to the ventral surface of the body a large number (from 

 twenty to thirty) of young leeches (Fig. 1,6). 



The young are attached to the ventral surface of the parent pos- 

 teriorly in a close cluster, which is surrounded on all sides by a vacant 

 space. Each adheres to the adult by means of the posterior sucker, 

 which is very distinctly marked and constricted off from the rest of 

 the body (Fig. 2, c.) The length of the young varies from about 

 jV to tV of ^1^ '^^^^ 'y *l^o color being light yellow or reddish, and the 



