PARENCHYMATOUS BLADDER-WORMS. 



343 



The state of matters in Cystitercu* pisiformis further shows us 

 that the excretion and accumulation of fluid in the interior of the 

 bladder- worms do not by any means always occur in the same com- 

 plete fashion. I have lately come to know of a number of Cysticerci 

 which had, strictly speaking, no bladder, since the accumulation of 

 water had either never occurred, or only to an extremely small extent. 

 They were all tape-worms without hooks, but I was unfortunately 

 unable to identify them. One of these forms is probably identical 

 with Diesing's Piestocystis varidbilis (Fig. 184). I observed it in the 

 lungs of the crow only once indeed, but in tolerable abundance. 



FlG. 184. Longitudinal 

 section of an unarmed cystic 

 worm from the lung of the 

 crow (Piestocystis variabilis, 

 Diesing?) (x 30.) 



FIG. 185. Unarmed cystic worm from the 

 body-cavity of Lacerta vivipara (Piestocystis 

 Dithyridium, Diesing). A, with head in- 

 vaginated ; B, with head half extruded ; 

 C, with evaginated head. ( x 30.) 



The bladder has an extremely thick wall, and is filled internally with 

 a mucous tissue which surrounds the narrow bladder-cavity on all 

 sides. Two other allied forms one from the sub-epidermal tissue of 

 the nightingale, and another (Fig. 185) from the body-cavity of Lacerta 

 vivipara (Piestocystis Dithyridium, Diesing) are wholly destitute 

 of a bladder-cavity. The interior of the body consists of an interlaced 

 connective substance, which is only so far variable in that its con- 

 sistency decreases towards the centre. With the loss of the bladder- 

 cavity, most of the characteristic peculiarities of the bladder-worms 

 have been also lost, so that it is hardly possible to distinguish these 

 forms fronf developed bladder-worms with evaginated heads. In 

 fact, even in spite of the attached caudal bladder, such a form as that 

 represented on Fig. 185, C, looks exactly like a young, still unseg- 

 mented tape-worm. 



