ON A CESTODE FROM CESTHACION. 407 



straight forwards as a cylindrical tiibe with irregular dilata- 

 tions. As this part of the oviduct contains fully formed 

 eggs, and is something more than a mere passage, it will 

 be convenient to designate it ootype, or primary uterus. 

 Anteriorly it opens into the secondary uterus by a longi- 

 tudinal slit, the extent and position of which vary in different 

 specimens, situated on one side of the vagina. 



After it becomes joined by the main vitelline duct, the 

 oviduct changes its structure, the cuticular hairs are lost, 

 and there is no epithelium, the wall of the duct now con- 

 sisting of cuticle, muscular la3'er, and layer of myoblasts. 



The uterus (figs, o, 6, and 18, s. ii.) is a cylindrical un- 

 divided chamber, extending from the level of the repro- 

 ductive aperture to the interspace between the anterior 

 portions of the lateral wings of the ovary. It has a lining 

 membrane composed of a single layer of cells. It has no 

 natural external aperture, but dehisces by the formation of a 

 longitudinal slit along nearly the wdiole, or only a limited 

 part of the length of its ventral surface. This dehiscence 

 readily takes place when the specimen is manipulated, more 

 especially when it is placed in sea -water, when the eggs are 

 observed to be suddenly discharged with the appearance of 

 a white cloud.' 



The shell-gland is a compact oval body, 'IS nun. in length, 

 Avhich surrounds the oviduct where the vitelline duct joins it. 



' Shipley, in his description of Uie worms collected by Dr. Willey (19), in 

 referring to a species of Pliy lobotlirium, states that in the oldest pro- 

 glotlides tiie uterus had ruptured "about the centre of tiie dorsal surface." 

 But there can be no doubt that the surface on which tlie dehiscence takes 

 place is the ventral, and not the dorsal. This is made perfeclly clear in the 

 case of the (/cstracion species by the relative positions of the various parts of 

 the reproductive ap|)aralus — as, for exam|)le, the vagina and vas deferens — 

 and by the disposition of the longitudinal vessels of the excretory system. It 

 may be remarked, however, that, in tlie Australian land I'lanarian (Geo pi an a 

 Mortoui) Steel has confirmed by observation on the living animal Dendy's 

 description of the rending of the dorsal body-wall on the discharge of the egg- 

 apsules CProc. Linn. Sue. N.S.W.,' I'JOO, p. 573, pi. M, fig. 10, and pi. 41, 

 fig. 6). 



