TRANSMIGRATIONS AND METAMORPHOSES. 247 



eggSj and are conveyed to another animal. The trichinae 

 are sexually developed in the same animal in which they 

 have been engendered. 



Worms which produce eggs do not usually hatch 

 them in the same animal ; they are evacuated with the 

 feces. The trichinae are an exception. These agamous 

 worms, when mtroduced into the stomach, rapidly pass 

 through their evolutions there, become sexual, lay eggs, 

 and the germs which are produced from them pierce the 

 tissues, and become encysted in the muscles or other 

 closed organs. It appears that the Ollulaniis tricuspis, a 

 nematode of the cat, presents the same phenomena. It 

 is a species of trichina, which lives at first in the 

 muscles of the mouse which serves it as a vehicle, then 

 in the stomach of the cat, where it becomes sexual and 

 complete. 



The Spiroptera obtusa is a worm remarkable for its 

 peregrinations. It passes with the excrements of the 

 mouse into the larva of Tenehrio molitor, which is very 

 fond of it. At the end of a month it is encysted in this 

 insect, and after five or six weeks it becomes sexual in 

 the mouse. The Splroptera obtusa of the mouse lays 

 eggs w^iich are evacuated with the feces ; and these 

 become, with the eggs w^iich they enclose, the prey of 

 meal worms, the larvae of the Tenebrio molitor, a coleop- 

 terous insect. These germs come forth in the intes- 

 tine of the larva, they perforate the intestine and 

 become encysted in the folds of fat which surround it. 

 Some fine day the insect is swallowed by the mouse, and 

 the Spiroptera, set at liberty in the intestine, wiU be 

 gradually matured until its sexual development is 

 complete. 



