PARASITES FREE DURING THEIR WHOLE LIFE. 129 



recourse only to leeches. Since we have seen these 

 insects harnessed and performing their exercises in 

 public, we cannot say that the future may not reserve 

 for us a still greater surprise. 



None who saw them can have forgotten the exhibition 

 of learned fleas made by a young lady who had sufficient 

 patience to train them. Walckenaer saw them in Paris, 

 and examined them with the eye of an entomologist ; he 

 relates that thirty fleas performed their feats at evening 

 exhibitions, for admission to which the sum of sixty 

 centimes was paid ; that these fleas stood on their hind 

 legs, armed with a pike, which was a very thin splinter 

 of wood ; some dragged a golden chariot, others a cannon 

 with its carriage, and all were attached by a golden 

 chain on the thighs of their hind legs. 



It is curious to see how Leeuwenhoek described, two 

 centuries ago, the history of the flea, with all its details, 

 the accuracy of which can scarcely be surpassed. He 

 observed their entire anatomy, as far as was possible 

 with the instruments of his time (1694), and his descrip- 

 tions are accompanied by excellent plates ; he saw them 

 copulate and lay eggs, and followed their whole develop- 

 ment. 



The finest fleas, both as to their size and form, inhabit 

 the bats. Fleas are often found on horses. A colonel 

 of cavalry, on his return from the frontier in 1871, sent 

 me some of these insects, with the request that I would 

 examine them. He added that the horses of his 

 regiment were literally eaten up by them. It was the 

 Hematopinus tenuirosins. There is a species peculiar 

 to monkeys, which Mons. Paul Gervais has described 

 under the generic name of PecUcinus, 



