438 ^ERO-SPIRANTT/V. 



Division .ERO-SPIRANTIA. 



WE have now arrived at that division of the order 

 Isopoda which comprises the species that differ from 

 the great majority of those animals, and indeed (with the 

 exception of the land-crabs) from the remainder of the 

 class Crustacea, in the manner in which respiration is 

 effected ; these animals residing, not in water, but in 

 damp situations, and breathing air, which, however, it is 

 necessary should be saturated with moisture, as has been 

 fully proved by a careful series of experiments published 

 by Messrs. Duvernoy and Lereboullet in the " Annales 

 des Sciences Naturelles," 2nd series, Zool., torn. 15, 

 p. 205. The specialized structures by which this is 

 effected will be noticed below. We must here, however, 

 refer to the exceedingly interesting genus, Tylos of 

 Latreille, founded upon an Egyptian species elaborately 

 illustrated by Savigny in the great work on Egypt 

 (Crust, pi. 13, f. 1), in which respiration is effected in a 

 double manner, namely, by the action of the water or 

 moistened air on the external surface of the respiratory 

 branchial plates or false legs on the underside of the 

 tail, in the same manner as in the Idoteae and other 

 normal Isopods, and by the inspiration of air by means 

 of certain spiracular orifices on several of the basal pairs 

 of these same appendages. We have searched in other 

 genera for these peculiar organs, but without hitherto 

 being successful. 



The division, which corresponds with the family 

 Cloportides of Latreille and Milne Edwards, comprises 

 the single 



