PROTEOCEPHALUS AMBLOPLITIS LEIDY 187 



SESSIONAL PAPER No. 39b 



LaRue for the species P. filaroides; PI. XXI, Fig. 14, shows a typical group of flame- 

 cells connected to the smaller excretory vessel (vide supra). While it was rather 

 difficult to make out the exact point where the common duct emptied into the 

 longitudinal excretory vessel, it could be seen that more flame-cells poured their 

 excretions into the smaller vessel than into the larger and more irregular of the 

 two. The stellate appearance at the ends of the flame-cells in this figure seems to 

 be due to contraction of the cell-body and the staining of numerous radiating 

 strands in its protoplasm, which do not appear in sections stained lighter. The 

 parts of the flame-cells itself are seen in PI. XXI, Fig. 15. The outlines of the 

 cell-body are difficult to discern, but they are quite irregular, as shown, the pro- 

 toplasm being prolonged into many processes of different lengths. Very little 

 structure can be detected in the protoplasm, but it is evident that vacuoles observed 

 bv various authors are present. The nucleus is comparatively large and stains 

 deeply. The ciliary flame is rather large and attached at its proximal end to a very 

 deeply staining body situated close to the nucleus, doubtless the basal granules 

 of the individual cilia ma-ssed together, which, by the way, are difficult to separate 

 optically. The conical cavity in the cell which accommodates the ciliary flame is 

 easily seen and has peculiar elongated thickenings in its walls, much resembling 

 elongated nuclei but which show practically no structure. The cavity itself is 

 directly continous with the very thin-walled, homogenous canaliculus which 

 connects it with those of its neighbours to the longitudinal excretory vessels. 



End Organ. — In his description of the scolex of P. ambloplitis Benedict 

 makes the following statement: "Directly beneath the apex of the scolex is a sac 

 of cuticular structure enclosing a small number of circular masses, closely packed 

 together. The masses seem to be of a calcareous nature and are penetrated by 

 numerous fine canals. No cormection whatever could be traced between this sac 

 and any outside system, although the excretory ducts form a thick network around 

 it." Longitudinal sections of the two scolices of sexually mature specimens showed 

 two conditions of this end-organ (PI. XXI, Figs. 16 and 17) which are very suggest- 

 ive. In both cases the organ, although not separated from the surrounding paren- 

 chyma by a clear zone as in LaRue's account of P. filaroides, is quite distinct from 

 the latter. Evidently Fig. 16 represents a younger stage than does Fig. 17. 

 In the latter it is to be noted that the whole of the central tissue has lost its struc- 

 ure, remaining as so much connective tissue, irregular muscle-fibres and other 

 deeply-staining bodies; the granular nature of the organ is more evident and the 

 material seems to be arranging itself into definite areas, doubtless to form the cal- 

 careous bodies above mentioned. The connection between the cuticula and the 

 organ is much less evident; the muscular bounding fibres, which are continuations 

 of the longitudinal muscular layer of the body of the worm, are losing their connec- 

 tions with the musculature beneath the cuticula; in fact the whole organ and its 

 surroundings seems to be in a degenerated state. On the other hand, PI. XXI, 

 Fig. 16, presents what one might consider a more functional structure. Although 

 there is no direct aperture through the cuticula of the scolex connecting the organ 

 with the exterior, it is quite evident that at a slightly earlier stage such might be 

 found. The muscular boundary is more definite, and the contents of the organ, 



