No. r.] SPHYRANURA OSLERT. 7 



body. The worms by no means confine themselves to any one 

 spot of the integument, but may move rapidly from one part of 

 the body to another, especially if disturbed. When the mouth- 

 sucker is not applied to the skin of the host the creature 

 exhfoits most lively changes in form, becoming extremely 

 slender, and waving from side to side, or retracting itself into a 

 short, rounded clump. 



If surprised, the worms are readily removed from the host 

 by means of forceps, or even on the point of a needle ; but if 

 the first attempt be not successful it becomes a matter of 

 greater difficulty to remove them intact. Should they become 

 free in a large quantity of water their swimming powers are 

 soon seen to be considerable, and they can progress, leech-like, 

 along the wall of a glass vessel by alternate fixation of the lips 

 and caudal suckers. Placed in a drop of water on a glass side 

 the worm soon fixes its caudal lamina firmly to the glass, and 

 it becomes difficult to detach it for examination from the ventral 

 surface, unless one has first placed the creature on its back, 

 and secured it in that position by a thin cover-glass. 



The generic name Sphyranura was suggested by the shape 

 of the caudal lamina, which is somewhat like a double-headed 

 hammer, the handle being formed by the long slender body. 

 (Fig. I.) When the caudal lamina is not fixed to any surface 

 it rarely rests in this shape, the two suckers being frequently 

 approximated to each other, so as to bring the opposite thin, 

 hook-bearing edges of the lamina in contact. Just as little does 

 the anterior end constantly retain the form represented in the 

 figure. The upper lip is atone time protruded in almost cylin- 

 drical form ; at another retracted so as to form with the lower 

 lip a circumoral sucker. 



One can readily distinguish the worms in which the single 

 ripe egg is present, its size being such, especially when the body 

 assumes its slenderest form, as to cause a distinct swelling op- 

 posite the uterus ; the opaque yolk glands are readily detected ; 

 they partly conceal the intestinal tubes, but leave uncovered the 

 central transparent testicular area, between which and the open- 

 ing of the genital sinus are the ovary, uterus, and genital ducts. 

 In front of the genital sinus can be seen the bowl-shaped 

 pharynx in constant activity, having free play in the surround- 

 ing prepharynx into which the mouth opens. On first exami- 



