FILAKIA f^RACILIS. 93 



worm, to repeat the process of generation, expulsion of ova, and 

 return to the system again. Let us now see how this matter is 

 managed in the case of the Tape-worm : here the process is not 

 quite so simple, for the process of metagenesis, as it is called, 

 holds among Tape-worms ; according to this law, the father does 

 not resemble the son, neither does the son again resemble his 

 son, but the son's son resembles the grandfather, so that the egg 

 of the Tape-worm may find its way into the system as in the 

 case of the round worm, but here we have — 



1. The egg. 



2. The larva, or embryo. 



3. The further developed larva, or Cysticercus cellulosoe, 



constituting the "measles" in pork. 



4. The undeveloped Tape- worm. 



5. The truly developed Tape-worm ; and 



6. The egg again, thus completing the cycle of generation, 

 expulsion of ova, and admission into the body as 

 before. 



Let us now consider 



Secondly, — The manner in [which these worms before us 

 obtained admission into the peritoneal sac; and by the light of 

 previous remarks bearing upon this part of the subject, I trust 

 we shall see our way clearly to a right conclusion. 



T^ow Dr. Watson, in his valuable work on '' The principles 

 and practice of physic" in respect of this matter, in the case of 

 Lumbrici, and I believe Ascarides also, details instances in some 

 degree resembling the case with which we have to deal, in which 

 he states that Lumbrici have made their way into the peritoneal 

 cavity, or great cavity of the abdomen, and also into the bladder 

 and other parts of the body otherwise than their usual habitat^ 

 and, contravening the vulgar opinion that the worms had eaten 

 their way through the coats of the bowel, he expresses his belief 

 that they have passed through accidental openings, e.^ , fistulous 

 passages, the result of ulceration followed by perforation of the 

 walls of the canal or viscus; he does not, however, state definitely 



