[cooper] TREMATODES FROM MARINE FISHES 201 



mm. in length. The general features are shown in Fig. 22, which is of 

 that from the intestine of the Bass (35.6mm. long) above. The capa- 

 cious anterior sucker, which occupies the whole of the diameter of the 

 anterior end, is truncate forward and flattened ventrally, the two 

 surfaces meeting at right angles. Its aperture opens on both surfaces, 

 but most of it is directed ventrally. The oral sucker is situated in 

 the mid-ventral surface and leads by a short, forwardly directed* 

 oesophagus into a comparatively small, ellipsoidal intestine which 

 extends "in front and behind the mouth." The ovary is on the right 

 side, behind the oral sucker, while the testes lie "in à line behind the 

 ovary," directed obUquely with reference to the longitudinal axis of 

 the body. The large penis-sac on the left side of and behind the 

 testes opens on the ventral surface some distance from the posterior 

 tip where the opening of the excretory system is located. The vitel- 

 laria are lateral to the intestine. 



What were considered to be early stages of this species were found 

 in small, elongated and transparent cysts, averaging 0-33 X 0- 15mm., 

 in the muscles of young M. dolomieu and Amhloplites rupestris, as- 

 sociated with encysted Cryptogonimus chyli. They were also found in 

 the muscles of young Perca flavescens and a Minnow, the species of which 

 was not determined at the time of making the dissection. The 

 largest, when removed from the cysts, very closely resemble the 

 smallest of those found free in the slime of the stomach, intestines or 

 coeca of the above-mentioned hosts. The smallest (Fig. 23) are very 

 simple in structure, most of the body being occupied by a large opaque- 

 white mass (in fresh material) with an apparent appendage towards 

 one end at the side. In sections the former was found to be the 

 intestine, while the latter is the beginning of the penis-sac and not the 

 first appearances of the excretory vesicles, as might be expected from 

 a comparison with encysted C. chyli. The intestine is lined with 

 cubical, nucleated cells, and connects by a thin-walled, short oesoph- 

 agus with the very small oral sucker, which with the anterior sucker 

 can be faintly seen in living examples, especially from a lateral view. 

 The excretory system appears in sections at this stage as an extremely 

 thin-walled tube, extending from a point at about the level of the oral 

 sucker to the posterior tip of the body where it opens by a minute pore. 

 No certain indications of the extension of this tube are to be seen in 

 the anterior parts of the body where in the adult it is well developed 

 "between the vitellaria." Later stages show that the process of devel- 

 opment involves a gradual enlargement of the suckers, the anterior 

 much more rapidly than the oral, and of the penis-sac, and the ap- 

 pearance of the anlagen of the genital glands, accompanied by an 

 absolute reduction in the size of the intestine, cf. Figs. 22 and 23, both 



