JOURNAL OF ENTOMOLOGY AND ZOOLOGY 163 
ing habit of the isopod and the hopping habit of the Amphi- 
poda. Such a distinction is not entirely valid however, since 
neither of these characteristics is common to all the forms of 
either group. 
The Isopoda body is differentiated into: (1), a head having 
sessile, usually compound eyes which may be contiguous or 
distant; antenne of two pairs, generally; a set of delicate 
mouth parts, consisting of an upper and lower lip, two pairs 
of maxilla, a pair of mandibles and a pair of maxillipeds; (2), 
a thorax of seven segments of similar structure, each bearing 
a pair of legs; the legs are often similar, a characteristic which 
led Latreille to name them Isopoda from two Greek words 
meaning ‘‘equal’’ and ‘‘foot’’. Latreille, however, was not 
acquainted with the many exceptional forms such as the modi- 
fied first leg for grasping purposes or the posterior swimming 
legs found in some species; (3), an abdomen consisting usually 
of six segments, five of which bear pleopods (respiratory and 
natatory organs); the sixth with a pair of uropoda (natatory 
organs). The Isopoda do not develop through a series of larval 
stages but through direct development. The females are pro- 
vided with marsupial plates which form a brood pouch in the 
sexually mature individual. 
After a careful study of the complicated and finely adjusted 
structure of these creatures one must have gained a great 
respect for them and for the complete and perfect results which 
nature has here effected. Add to this study a knowledge of the 
actual service rendered by the Isopoda in the economy of 
nature and one’s interest in them will be increasingly greater. 
Have you ever stopped to consider how very rich in life the 
sea is, with its multitudes of marine plants and animals? Have 
you further considered how many of these forms are constantly 
being destroyed in one way or another and subject to the pro- 
cesses of decay? If so, you have often wondered how the sea 
is kept ever sweet and pure. For a solution, in part, of this 
question I would ask you to turn to the isopods and their asso- 
ciates, the amphipods. These small animals, many of them al- 
most microscopic in size, are the scavengers of the waters and it 
