PARASITES. 101 



I had commenced tlie study of encysted Tetrarliynclii 

 in the peritoneum of the Gadidiie m 1837. Ten years 

 afterwards, shortly after a visit from my learned friend, 

 Mons. Kolliker, I discovered that this world of parasites 

 did not live such a monotonous life as was supposed. 

 I ascertained by my dissections of fishes, that the 

 tetrarliynclii also, which were supposed to be disinherited 

 by Nature, knew how to vary their pleasures ; that 

 instead of spending their whole life in a prison cell, they 

 change their home at a certain age, and pass the latter 

 part of their existence in more spacious habitations. 



I had seen the Tetrarhynchus agamus inhabiting a 

 cyst in the peritoneum of the gadidae, and I had met 

 with the same tetrarhynchus completely developed and 

 sexual in the spiral intestine of the voracious fishes 

 known under the name of squalidse, or sharks. This 

 caused me to write to the Academy of Brussels, at the 

 meeting on January the 13th, 1849, that the order of 

 vesicular worms, admitted by all helminthologists, ought 

 to be suppressed. 



These worms began to be understood when these 

 cysticerci ceased to be regarded as sick creatures. 

 Siebold had mistaken the creche for the hospital, and 

 instead of seeing in the cysticercus a young animal full 

 of life and of the futm'e, he looked upon it as a gouty 

 individual, ready to breathe its last sigh. 



These fish had dkected me m the right road ; I had 

 closely followed up certain very characteristic worms, 

 which lived under a very simple form in certain fishes, 

 and which, passing with then- host into the stomach of 

 another, finished in the latter their toilet and their 

 evolution. I had been a witness of all their changes 



