JOURNAL, OF ENTOMOLOGY AND ZOOLOGX 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; antenna? 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 iiair 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 

 accpuiinted with the many exceptional forms such as the modi- 

 fied first leg for grasping purposes or the jiosterior 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 jiro- 

 vided with marsupial plates which form a brood jjouch in the 

 sexually mature individual. 



After a careful study of the complicated and finely adjiisted 

 structure of these creatures one must have gained a great 

 respect for them and for the comi)Iete and perfect results which 

 nature has here effected. Add to this study a knowledge of the 

 actual service rendered b}^ the Isoi)oda 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 f 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 isoi)ods 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 



