1.^0 T. P.. IIOS^JKTKR (~)X A XRW CV^TTCKRUS FROM CYCLOPS AOrUR. 



Anas fusca in Nov., 1867, lie found the liooks on the rostrum 

 measured 0*043 m.m., which closely corresponds with my speci- 

 mens. The rostrum was partially inva^inated in the connec- 

 tive tissue of the head. 



The suckers (Fig. 26) were arranged, as usual, equidistantly 

 round the scolex, and, although they were in an advanced stage 

 of formation, they were deficient in the muscular rigidity 

 which, in. the perfect scolex, enables them to adhere to the 

 mucous membrane of the duodenum of their vertebrate host. 



The neck (Fig. 2c) was short, constricted and bulbous in 

 contour, and it was attached to the cyst by the fibrous tissue of 

 the immature primary proglottis, which latter was partially 

 within the operculum of the cyst. 



In neither specimen could I trace the six hooks of the 

 hexacanth stage, as is usual, on the caudal appendage ; in both 

 cases this was very short, but I am doubtful if this is the 

 normal condition. 



Cysticercus ? (E/Osseter). 



Form of cyst, oval. 

 Length of cyst, 0*282 m.m. 

 Width of cyst, 0*255 m.m. 

 Hooks, 8. 



Length of hooks, O'OSO m.m. 

 Habitat, Gy clops agilis. 



I took this Cysticercus (Fig. 4), the only one I have captured, 

 from the perivisceral cavity of Cyclops agilis^ obtained from 

 the same pond as before. 



The cyst is oval, striate, and very symmetrical in its contour. 

 The invagination commences Yerj abruptly, and there is a deep 

 crateriform depression at this portion of the cyst (Fig. 4e). 

 The cuticular or fluid cavity (Fig. 4c) is very deep, more 

 especially the posterior or basal portion, where the caudal 

 appendage h enters the cyst. . This it does through a ring- 

 collar aperture (Fig. 4^), spreading out inside the aperture 

 where it coalesces with, and forms an integral part of, the 

 hypodermis or lining membrane of the cyst (Fig, 4:d). The 

 parenchymatous tissue was homogeneous in character, so much 

 so that it was impossible to differentiate the usual outlines of 

 rostrum, scolex, and suckers in the formative substance. The 



