— 11 — 



It is Seen from the above review of the literatiu'e that, although the organs of respiration 

 of the Oniscidae have been the subject of investigation by a cousiderable niunber of zoölogists, 

 scarcely anything conceruing their more intimate characters can be said to have been finally set- 

 tled. Leaving out of account the aben-ant views of Treviranus and Brandt, the only poiut as to 

 which there had been some approach to iinanimity of opmion was that the corpora alba are organs 

 containiug aü'. Even as to this Dm'EKNOY and, at the time of the publication of their Joint work, 

 his collaborator, Lereboullet, were at least in doubt. They record that they observed a clear 

 liquid to pass out from tlie aperture associated with the corpora alba, and their final conclusion 

 was that the organ served to abstract the moistiu'e from the air. 



As to the precise structure of the same organ, the statements of the several authors are 

 widely divergent. In its general featiu-es it has been compared variously to a tree, a sponge and 

 a net-work. As to its physiological natura it has been regarded at times as a foi-m of trachea, 

 again as a limg, and again as a modified gill. 



The only histological investigation made has been that of Leydig and the conchisions 

 reached by him, in regard to the corpora alba, were contradictory, in respect to uearly all essential 

 points, to those reached by his predecessors. Moreover, a reading of Leydig's article shows that 

 as an histological study it is incomplete. 



The investigations hitherto made upon the special modifications of the outer divisions of 

 the respiratory appendages have been confined to the genera Forcellio and ArmndüUdium. It has 

 not been hitherto discovered that also in the genus Oniscus there are highly specialized structures, 

 though quite different in their morphological characters, adapted to the Performance of the respira- 

 tory function in air. 



It is evident that a thorough investigation, employing the resources of modern laboratory 

 methods, was to be desired in order to add to our knowledge of these interesting organs. The 

 writer believes that the woi"k here submitted is a contribution to that end. 



