254 W. S. NiCKERSON, 



vesicle are delicate circularly arranged fibers biought out as black 

 lines or dots by the iron haematoxylin staiii. From these charac- 

 ters it appears tliat the wall of the caudal vesicle is structurally 

 mnch more like the external body covering- thau like the excretory 

 vesicle. 



The septa seen in cross section iinder high magnification 

 present an appearance very feather like, the axis (or shaft) beiiig 

 made of a double layer of basement membrane from which stand 

 out on each side long slender columnar processes side by side like 

 the barbs of a feather. These barb like processes are a little too 

 broad and blunt at the ends to be cilia and have a vagueness of 

 outline which makes it impossible to say just how distinct from one 

 another they are. They show no trace of nuclear structure. As 

 seen under low magnification they appear as zones of finely granulär 

 material rather broad on the sides of the septa and thinner on the 

 walls of the vesicle between the bases of the dififerent septa as 

 indicated in a part of Fig. 5. It is impossible to say with perfect 

 assurance what the nature of this material is, but the Impression 

 which it gives when studied with high powers is that of a degener- 

 ated epithelium in spite of the absence of any trace of nuclei and 

 the quite unequal thickness in the ditferent portions. If it be 

 regarded as a degenerated epithelium the condition olfers an iuter- 

 esting comparison with that found by Peatt (1898) in the uneverted 

 caudal appendage of ApoUema. This Interpretation also is in 

 harmony with the view that the cuticular body covering of the 

 trematode has the morphological relations of a hypertrophied base- 

 ment membrane of an epithelium which has disappeared in embryonic 

 stages. 



It is seen from the foregoing description that C. vesicaudus differs 

 anatomically from the type species C. lenoiri in three respecta, viz. 

 the possession of the caudal vesicle, the absence of an esophagus 

 and the oblique position of the festes. These dilferences would 

 perhaps justify the creation for it of a new genus. Staffokd's species 

 C. americaniis Stands intermediate between the other two, agreeing 

 with C. vesicaudus in the oblique position of the festes and with 

 C. lenoiri in the possession of au esophagus and the lack of caudal 

 vesicle. If a new genus were created it would therefore has based 



