82 A FURTHER KNOWLEDGE OP THE CYSTIC CESTODES, 



through a pedicel and emerging at the apex, apparently beside the 

 bothrium proper; neck vei-y long and slender, cylindrical, enlarging 

 slightly at the contractile bulbs and rounded at the base, tapering 

 to a point where it is connected with the body (blastocyst) ; proboscis 

 sheaths spiral, contractile bulbs linear, oblong : booklets long and 

 slender, falcate. Size of scolex 4-60 mm. Hooks near the middle 

 •06 mm. long. 



(1) The so-called blastocyst or endocyst is the serial homologue 

 of the caudal vesicle of the Cysticerci. 



(2) The wall of the invagination sac represents the body of 

 these forms. 



(3) The scolex, consisting of head and neck, arises from the 

 bottom of the invagination sac as a knob-shaped process, which, 

 by subsequent elongation and internal differentiation, gives rise 

 to the fully-formed scolex. 



EXPLANATION OF PLATES. 



Plate hi. 



Figs. 1-6. — Piestoeystis Hoplocephali. 



Fig. L — Transverse section of the wall of Hoplocephalus cyst. Zeiss. D., 

 oc. 1, cam. luc. h. I., homogeneous inner layer of wall (" blas- 

 togen ") ; I. I., middle laminated zone ; /. I., outer fibrous layer. 



Fig. 2. — Longitudinal section (nearly median) of Cysticercus from Hoplo- 

 cephalus, with partially evaginated head. From a specimen 

 preserved in eorr. subl. and stained with cochineal. Zeiss. A., 

 oc. 1, cam. luc. /. .?., frontal sucker; h. c, bladder cavity ; l.f., 

 longitudinal elastic fibres ; t. c, terminal canal of excretory 

 system. 



Fig. 3. — Transverse section of a Cysticercus with invaginated head, at the 

 level of the suckers. Corrosive sublimate and Ehrlich's Haema- 

 tnxylin. Zeiss. A., oc. 1, cam. luc. ; details with Zeiss. D. 



c, cuticle; s. c, subcuticula ; r. c, " receptaculum capitis"; 

 e. /., elastic fibres ; a. v., ascending vessel of excretory system ; 



d. v., descending vessel ; i. v., invagination cavity of head. 



