508 DEVELOPMENT AND GROWTH OF MNIA SOLIUM. 



dating from the year 1801, x are really the best researches on the 

 structure of Cysticercus cellulosce until modern times. He recognises 

 not only the connection between the head-process and the bladder, but 

 knows also that the former is hollow up to the circlet of hooks, and is 

 invaginated in itself, so that, when pressed, it can be protruded from 

 the opening of the bladder like a snail's tentacle. Nor does the exist- 

 ence of the above-described outer cavity escape him, although he does 

 not quite correctly grasp its relations to the receptacle, which even 

 Werner has recognised and described as a tunica vaginalis.* 



Although the head-process is in reality an integral part of the 

 bladder, and, until its separation, is in connection with the organs and 

 tissues of the latter, yet one must not directly identify the two por- 

 tions in their anatomy and histology. Both differ in fact widely, much 

 more indeed than do the head and joints of the adult tape-worm, 

 whose genetic relations are very similar. These differences include 

 more than the specific organization of the head-proper, and persist 

 between the bladder and the cylindrical body of the worm. 



What strikes us at once is the different thickness and firmness of 

 the body-wall. This is thin and tender on the bladder, but acquires a 

 considerable thickness, and a much firmer character when it is con- 

 tinued to the attached process. The connective-tissue becomes less 

 abundant, the musculature greatly increases, and the fibres form, as we 

 have seen, regular layers and bands. The calcareous corpuscles 

 embedded between the latter serve to increase the firmness of the 

 structure. Not less marked is the thickness of the cuticle, which is 

 fully four, or even six, times as great as that of the bladder, although 

 it turns its surface, not towards the exterior, but towards the interior 

 of the body of the worm. The subjacent subcuticular layer is also of 

 considerable thickness. It exhibits the same structure as the sub- 

 cuticula of the adult tape-worm indeed the cylindrical body of the 

 bladder-worm is in all essential features like the latter. 



1 " De Taenia hydatigena anomala," Dissert, inaug., Erlangen, 1801. As specially 

 characteristic, I may quote these sentences : " Taenise corpus in se ipsum retractum atque 

 mirifice involutum figuram globosam repraesentat " (p. 17). " Vermis corpus canalis mem- 

 branaceus, cavus, conice elongatus, et rugis seu plicis circularibus compositus est" (ibid.). 

 " Extremitas crassior superficiei internae vesicae caudalis imposita atque adnata aperturam 

 vesicae circuradat" (ibid.). " Taeniae corpus quiescent* in se ipsum inverse est retractum" 

 (p. 36). " Eodem modo vermis ex se ipso procedit, quo tentaculum Helicis in se conver- 

 sum atque retractum invertendo ex se ipso prodit" (p. 21). 



2 Loc. cit., p. 22. " Pars corporis vesicae adhaerenti proxima et in vesicae antrum 

 recedens globuli membranam exteriorem format (usque ad latus, ubi) corporis vermis 

 membrana in se ipsam intus est reflexa." See also the explanation of Fig. 8 "Tunica 

 vaginalia quam adesse opinatus est Werner, non est nisi pars ultima corpusculi taeniae sacci- 

 formis, quae superficiei internae vesiculse caudalis adhaeret ejusque continuationem inaequa- 

 lem reprsesentat." 



