INTEODUCTION. 



15 



toma offers, lie says, " une anomalie remarquable. Bien- 

 que leurs aiitennes soient evidemment conformees sur 

 un meme type, uon seulement le nombre de leurs arti- 

 cles est soiivent variable, mais ce nombre n'est pas 

 toujours egal dans le meme individu." This diflference 

 between the two antennse, even of the same specimen, 

 ought to have prevented him from characterising a 

 genus on such merely accidental characters. 



His last genus, Hypogastrura, is founded on the 

 Fodura aquatlca, for which species it seems better to 

 retain the old generic name. M. Bourlet also describes 

 a number of new species, and concludes with, some 

 general remarks on the habits of the group, which he 

 describes with considerable accuracy, though he is in- 

 clined to regard them as viviparous, which is a mistake. 



His other two proposed genera, Le^ndocyi^tus and 

 Isotoma, have been generally adopted. 



The following is a list of his species : 



