breathing-hole. These, are the gills, consisting of three pairs of sini|ilf membranous (häutige) leaves. 

 He then desciibes them in detail as to form. 



This ajjpears to l)e the iirst published descriptioii of the inner gills. 



Brandt' in 1833 expressed the same opinion as Treviranus as regards the nature of tlie 

 (irst two pairs of appendages in the genus PorceMio. 



Milne-Edwards ^ in 1839 annonnced that he had confirmed throngh his own observations 

 the conclusions reached by Latreille. He stated that the branched air-canals were rightly to l)e 

 compared with the tracheae and lung-sacs of the Insects and Arachnids. 



The sanie author in his H i s t o i r e naturelle des C r u s t a e e s , published the nest year, 

 says concerning the 01o])ortides terrestres : "Mais le caractere le i)lus important . . . est fourni par 

 le mode de conformation des fausses pattes abdominales des deux ou quatre premieres paires. Oes 

 appendices servent ä la respiration comme chez tous les autres Isopodes ; mais au lieu de constituer 

 des branchies, ils remplissent les functions de poumons, car ils renferment des organes creux dans 

 l'interieur desquels l'air atmos])heri(|ue penetre directement ;i travers des ouvertures diversment 

 disposees." 



A niore thorough study than any hitherto made was that of Duvernoy and Lereuoullet 

 ]iublished in 1841.^ Tiiese authois give a detailed account of the general anatomy of the respira- 

 toiy organs of the land-isopods and also describe a series of experiments made upon Pom-Uio and 

 ArmadiUio to determine their comparative vitality in dry and in moist air, in water and when ex- 

 liosed to the direct rays of the sun. 



The foUowing is a simimary of the conclusions reached liy thcse investigators : 



The external organs are composed of two leaves (the outoi- of much greater ronsistence 

 tlian the inner) the Space 1)etween which has a double communication with the blood System, re- 

 ceiving on the one band l)lood to be respired and on tlie other giving back that respired. 



The "corps ])lanc" is not present in all the Cloportides as Latreille had annonnced'' l)ut 

 only in the genera PorrcMo and Arynddillis. In these two genera it is constant in the fii'st two 

 jia.irs of lames operculaires and in two species, PorcelUo uriiiadilloide and Porceüio ä trois handcs, in 

 all fivc pairs. 



The corps blaue has a tree like, spongy and vascular appearance. It is a simi^le modi- 

 ticatiou of the lames branchiales operculaires, through the inward folding and division of the mem- 

 branous leaf of the lames. 



It absorbs the moisture of the air and maintains the moistened condition of the lame 

 l)ranchiale [the inner gill]. 



On the posterior borders of the lames enclosing the corps blanc is a cleft which one of 

 the authors had observed to dilate and contract and out of which they had seen a fluid to pass. 

 „II s'en echappe, suivant notre Observation commune, de tr^s petites quantites de liquide aißieux 

 dans lequel du moins, nous avons constate (ju'il n'existe pas des globales." 



' Medizinische Zoologie, II. Band, Bei-lin, 1833. 



'' L'Institnt, 1839. 



' Essai d'une Monograpliie des organes de la i-espiration de I'ordre des (Jmstaces Isopodes. Annales des seiences 

 naturelles. Ser. 2, Toiu. XV, 1841. 



•* In tliis Latreille was followed by Milnh-Edwauds. See, Hisloire naturelle des Crnstaoes, 

 184U. Bat in liis Physiologie C o m p a r e e , 1857, he refers to the eoriis blane as jiresent only in the two genera 

 named above. 



