BY J. P. HILL. 63 



The evaginate Cysticerci (Fig. 10) measure from 1"25 to 2 mm. 

 in length. In each can be distinguished an anterior or head end, 

 conical in form and provided with four large well-marked pro- 

 trusible suckers, which passes gradually, by way of a narrow neck 

 region, into the posterior much wider and longer region, which 

 Leuckart considers as the homologue of the caudal bladder of the 

 ordinary bladder worms. 



The whole body is invested in a layer of cuticle which in the 

 head region is covered by numerous very minute backwardly 

 directed spinules -002 mm. in length. Hooks are altogether 

 absent. Numerous minute black points are visible all over the 

 cuticle. These may be the external openings of pore canals, but 

 sections did not reveal their existence in the cuticle. The pos- 

 terior part of the Cysticercoid contains very numerous uniformly 

 distril)Uted calcareous corpuscles, which are most abundant in the 

 superticial layers of the body tissue, but occur in the more centra 

 tissue as well. They vary in shape from round to angular and 

 are almost entirely confined to the posterior region, only a few 

 being found between the suckers of the head. 



The excretory system opens at the posterior end of the Cysti- 

 cercus by a short tube, which in the living form is seen to be 

 pulsatile. It is lined by a continuation of the outer cuticle and 

 in sections is visible as a minute tube with a cuticular wall passing 

 forwards for a short distance. 



In the inverted Cysticercus the head lies inverted in the central 

 tihsue of the body, and, as in the typical bladder worm, the cavity 

 of invagination is in free communication with the exterior, and 

 into it the cavities of the four suckers open. Fig. 11 represents 

 a transverse section at the level of the suckers. Just as in the 

 case of the Hoplocephalus Cysticercus, the invaginated head is 

 surrounded by a thick envelope of circularly arranged tissue 

 representing the receptacle of the head. In the superficial region 

 of the body tissue in the posterior part of the Cysticercus, and 

 especially clear in Cysticerci preserved in Flemming's Fluid, are 

 bundles of elastic fibres which run towards the head, and as they 



