1914] A New Cestode from Amia Calva L. 95 



expands to form a vesicle, varying in diameter from 25 to 55 ^ and is 

 situated immediately within an invaginated portion of the cuticle into 

 which it opens. The openings of the lateral vessels are very difficult 

 to make out, since they seem to be quite closed in many cases. All 

 stages between the condition shown in Fig. 12 and one (in small scolices, 

 Fig. 6) in which all three vessels opened separately on the concave 

 posterior surface of the strobila, were observed. Thus it would appear 

 that this species bears out Leuckart's view that the relations between the 

 posterior openings of the excretory system are developed after some part 

 (in most cases an earlier proglottis) has been separated from the strobila. 

 In fact Fig. 12 is quite suggestive in all of its parts of a simple contraction 

 of the hinder end of the worm to form a cuticular invagination, all of the 

 vessels formerly opening on the outside. 



The flame-cell (Fig. 13) is quite typical in structure and closely 

 resembles that of the genus Proteocephalus Weinland, which has 

 been studied by the writer, in that the vestibulum in which the 

 "ciliary flame" is located is provided with peculiar darkly-staining 

 longitudinal thickenings which do not seem to be mentioned in the 

 literature on the excretory system of the cestodes. Their significance is, 

 of course, merely conjectural. The cell-body is usually not as distinct 

 as that shown in the figure, since the cytoplasm is quite clear, but the 

 nucleus and basal body, as well as the "flame", are very easily made out 

 in sections. It was found impossible to trace with certainty the canal- 

 iculus from the flame-cell to any of the larger vessels or smaller canals 

 mentioned below. The flame-cells, themselves, are few in number and 

 arranged more or less radially close around the large vessels. 



The structure of the latter is shown to a certain extent in Fig. 14. 

 Although the wall is extremely thin, the following parts could be dis- 

 cerned with high magnifications: a thin cuticular layer, with a distinct 

 basement membrane, lining the tube; outside of that a clear line in 

 transverse sections and dotted in longitudinal sections, thus resembling 

 a layer of extremely fine cuticular muscles; and farthest peripherally, a 

 condensation of cytoplasm with nuclei slightly smaller than those of the 

 parenchyma, but hard to distinguish from the myoblastic nuclei near at 

 hand. The circular striations appear to be more protoplasmic than 

 muscular in nature and in many places cannot be differentiated from the 

 basement-membrane. 



Foramina secundaria are to be found in the anterior proglottides, 

 especially on the outside of the ring to which the appendages are united 

 (Fig. 35). The openings, themselves, are very minute (vide supra, under 

 the cuticula), but the course of the capillaries leading to them through 

 the subcuticula and peripheral portions of the cortical parenchyma is 



