ZooL.— Vol. III.] HEATH— EPIDELLA SQUAMULA. Ill 



in all essential respects these organs appear to resemble the 

 sucking- pits (Sauggruben) of many trematodes, especially 

 E. hippoglossu as figured by van Beneden (1861). The 

 cells of which they are composed are chiefly columnar, 

 and appear to be devoid of any cuticle upon their free 

 extremities. Their opposite ends frequently become pro- 

 duced into from one to three processes, from which delicate 

 fibers, probably nerve, extend far into the tissues of the 

 body. Muscle fibers may be detected among the bases 

 of these cells, and also the long and slender ducts of a few 

 dorsally situated unicellular glands which apparently open 

 to the surface. The muscle fibers in every case appear to 

 be merely the termination of the great bands which are 

 located immediately beneath the cuticle on the dorsal and 

 ventral surfaces of the body. In specimens treated with 

 methyhn blue these somatic muscles, transverse, oblique, 

 and longitudinal, become clearly differentiated, and are then 

 seen to split up into a number of dehcate branches upon 

 approaching the margins of the body. This also occurs in 

 the region of the anterior sucking discs, and the latter appear 

 to be controlled wholly by these small fibers, and to lack 

 definite muscles of their own. 



The anterior sucking discs are brought into use as 

 adhesive organs chiefly when the animal is changing its 

 position and the posterior disc is unattached. Under such 

 circumstances they are sufficient for this almost instantane- 

 ous shifting, but compared with the great posterior sucker 

 their power of adhesion is relatively weak. It appears 

 probable, judging from their abundant nerve supply, that 

 they function principally as sense organs, as Braun (1887) 

 suggested several years ago. When disturbed, some indi- 

 viduals may be seen to wave the forward part of the body 

 about, and to touch it lightly to the host as if in search of a 

 more suitable place for attachment, a movement common to 

 many leeches. As in the latter, undulatory movements of the 

 body also occur, while both extremities of the animal are 

 attached, which probably aid in the process of respiration. 

 In £. squamula the posterior sucking disc (fig. i) is more 



