11 
It is seen from the above review of the literature that, although the organs of respiration 
of the Oniscidae have been the subject of investigation by a considerable number of zoologists, 
scarcely anything concerniiig their more intimate characters can he said to have been finally set- 
tled. Leaving out of account the aberrant views of Treviranus and Brandt, the only point as to 
which there had been some approach to unanimity of opinion was that the corpora alba are organs 
containing air. Even as to this Duvernoy and, at the time of the publication of their joint work, 
his collaborator, Lerebouleet, were at least in doubt. They record that they observed a clear 
liquid to pass out from the aperture associated with tlie corpora alba, and their final conclusion 
was that the organ served to abstract the moisture from the air. 
As to the ju’ecise structure of the same organ, the statements of the several authors are 
widely divergent. In its general features it has been compared varioiisly to a tree, a sponge and 
a net-woi'k. As to its ])hysiological nature it has been regarded at times as a form of trachea, 
again as a lung, and again as a modified gill. 
The only histological investigation made has been that of Leydig and the conclusions 
reached by him, in regard to the corpora alba, were contradictory, in respect to nearly 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 PorceUio and ArmadiUidkmi. It has 
not ])een 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 work here submitted is a contribution to that end. 
