72. A FURTHER KNOWLEDGE OF IKK CYSTIC CESTODES, 



enveloppe tres fragile, composee d'une vnince cuticule et d'une 

 couche sous-jacente de nature cellulaiie." This subcuticular 

 layer he describes as consisting of small groups of fine granules, 

 separated from each other by a hyaline border and evidently 

 representing a layer of cells in process of degeneration. Villot's 

 observations receive ample confirmation from the form under 

 consideration. There is here, just as in C. arionis, a layer of 

 cuticle externally, and an underlying cellular layei-, which, how- 

 ever, in the case of our Alonocercus, shows no signs of degeneration. 

 Accepting Moniez's view that the cyst belongs to the Cysticercoid 

 itself, what does it represent 1 With Villot I agree in regarding 

 it as the blastogen or blastogenic vesicle (proscolex), which by 

 internal differentiation, either by budding or some ])rocess of 

 separation, gives rise to the Cysticercoid proper. The Cysti- 

 cercoid, then, together with the outer cellular layer, the blastogen, 

 represent the entire product of the six-hooked embryo. 



We pass now to the consideration of the second part of our 

 Monocercus, the Cysticercoid proper. 



Each is an ovoid body measuring from 'IS-'Smm. in diameter. 

 It lies perfectly free in the centre of the surrounding layer of cells. 

 There is no connection nor any sign of connection between the 

 outer wall and the Cysticercoid. Villot* believes that in Cysti- 

 cercus arionis he has seen, at the posterior part of the caudal 

 vesicle of the Cysticercoid and the cyst, traces of an original 

 connection in the form of " une sorte d'ombilic ou de depression 

 infundibuliforme." No such indication of an original connection 

 is to be seen in the case of Monocercus Didymogastris ; if it ever 

 existed no trace of it remains in the fully-formed Cysticercoid. 

 This fact suggests that the Cysticercoid, instead of arising from 

 the proscolex by a process of budding, arises by the separation of 

 the more central cells from a peripheral layer. The latter forms 

 the outer layer of cells, while the central mass gives rise to the 

 Cysticercoid by difierentiation, probably in a manner similar to 



* Loc. cit. p. 38. 



