TRANSMIGRATIONS AND METAMORPHOSES. 213 



are cestodes peculiar to vegetable-feeders. As a feeder 

 on vegetable diet he also harbours vesicular agamous 

 cestodes, which are only found in him as passengers. 



The Tasnia serrata of the dog lives at first as a 

 passenger in the peritoneum of the hare and the rabbit ; 

 and every one knows how greedily the dogs eat the 

 viscera of these animals. 



The cat entertains another kind of tasnia, and, as we 

 may easily suppose, in its young state it lives as a 

 passenger in the mouse or the rat. Who then has 

 traced out for it this itinerary, and pointed out the way, 

 the only one by which the parasite can hope to take 

 possession of its proper abode ? Evidently it is neither 

 the tape-worm nor the cat. The plan for all these 

 various species is marked out beforehand, and each 

 animal as soon as it is born knows it without being 

 taught. 



A Danish naturalist, Mons. H. Krabbe, has just 

 finished a special, work on cestode worms, of the genus 

 Tasnia, and he remarks that there is no class in which 

 these worms are so abundant as in that of birds.- It 

 is among the rapacious and carnivorous birds of this 

 class that they are less abundant. Among mammals, 

 the carnivora possess the greater number. This fact, as 

 M. Krabbe remarks very rightly,- seems to indicate that 

 the cestodes of birds especially employ the inferior 

 aquatic animals as their vehicles when in their incom- 

 plete state. 



Let us consider the solitary worm of man (Tasnia 

 solium), it will enable us to understand all the others. 

 Known by the name of taenia, or solitary worm, it is, like 

 all the cestodes, a marvellous association of mothers 



