INTRODUCTION. 
Tue term “Sessile-eyed” has been applied to the order 
of crustaceous animals forming the subject of this work 
in contradistinction to that of the “ Stalk-eyed ” order, 
of which Professor Bell has given an account in a pre- 
ceding volume of this series. The name, with its Greek 
equivalent, Edriophthalma, was first given by Dr. Leach, 
and has been recognized by all subsequent naturalists. 
It must not, however, be understood to characterize every 
genus that should be classed in the order. Among the 
Isopoda, the genera of T’anais, Paraianais, Apseudes, and 
Munna, have their eyes fixed on pedicles. In the first of 
these genera, the structure differs so much in character 
from that of the normal Jsopoda, that it has been classed 
with the Stalk-eyed Crustacea by Fritz Miller and Anton 
Dohrn. In this work we have placed it in an interme- 
diate position between the Amphipoda and the Isopoda ; its 
most important structural characters holding a position 
nearer, but intermediate in relation between, these two 
orders than they bear to the Stalk-eyed Crustacea. 
While, therefore, the eyes may be considered (as they 
have been since the days of the Swedish naturalist, 
Linnzeus) as a ready and convenient means of classifi- 
cation, separating one great division from another, this 
character must be received as only an approximation to a 
ae2 
