1915] MacCailum: Ectoparasitic Trematodes 467 



adult worm. I have pieces three inches long and from my ex- 

 perience in trying to get a whole worm by putting the pieces to- 

 gether, I would say that I believe five or six inches the maximum 

 length. In the figures the worm is shown cut across, because 

 a whole adult worm has not yet been dissected out to make a 

 certainty about length. 



The worm sometimes seems to have all the organs, and the 

 uterus full of eggs, etc.; the form of body will then abruptly 

 change to a much narrower and thinner shape and to a milky 

 white color, with only a water vascular canal in the middle, run- 

 ning through the middle the entire remaining length, perhaps 

 for an inch or so, and coming to a fine point or be broken off 

 when not larger in diameter than a hair. 



In one of the young worms the esophagus and intestinal 

 ceca are plainly shown and are depicted in Fig. 138. As may 

 be seen in the figure, the esophagus extends from the mouth 

 about one-third of the length of the worm, when it divides into 

 two ceca which extend nearly to the posterior end of the worm. 

 No pharynx is seen. 



The mouth is an oval opening distinctly marked out. It is 

 slightly sub-terminal and may be observed when the worm is 

 on its back. The anterior ends of the uterus and vas deferens 

 plainly pass under the posterior edge or lip, and disappear in 

 the mouth, which must therefore be the outlet for their contents. 

 Eggs are seen in utero, a very short distance from the end, but 

 no mouth of the uterus can be seen. The tissues of the body 

 in this locality, as well as elsewhere outside of the organ, appear 

 to be a fine network of muscular fibers with small cells and fine 

 granular matter sparingly distributed. In some of the speci- 

 mens the head which is very small appears to be connected with 

 the body by a decided neck, but of course this varies as the 

 result of muscular action. No nervous system can be made out, 

 but a water vascular system is present and the small vessels 

 gradually coalesce towards the tail until the main vessel often 

 can be seen making a zig zag course to the outlet. 



The female genitalia, as far as can be made out, consist 

 of the ovary which is a thick somewhat curled tube extending 

 from near the anterior end to about the junction of the posterior 

 with the anterior two-thirds of the worm. It stains deep red 

 with carmine. In some specimens there is an enlargement a 



