102 MANUAL OF ANIMAL BIOLOGY 



1. Abdominal Appendages 



The last pair of appendages on the abdomen, the uropods, is 

 attached to segment xx. They are biramous and both the endo- 

 podite and exopodite are essentially broad, flat plates adapted for 

 use in swimming. 



Each of the next four abdominal segments (xvi-xix) on the 

 female bears a pair of typical, small biramous appendages. The 

 exopodite of each of these abdominal swimmerets consists of a flat- 

 tened, blade-like structure made up of several joints. The endo- 

 podite is similar in structure, but is somewhat larger. The abdom- 

 inal appendage on segment xv of the female is greatly reduced and 

 not functional. On the male the abdominal appendages of segments 

 xv and xvi are very atypical, being modified for the transference of 

 sperm. (W. f. 65.) 



2. Thoracic Appendages 



There are five pairs of uniramous walking legs attached to seg- 

 ments x-xiv, all of which are built on the same plan. The pro- 

 topodite is made up of the coxopodite and the basipodite. The 

 coxopodite bears the epipodite, with the attached gill filaments 

 which project dorsally into the gill chamber. The epipodite is 

 present on all the walking legs except the last pair on segment xiv. 

 The basipodite bears a five-jointed endopodite, the last two joints 

 of which may form a pincer, or chela. The pincers on the first pair 

 of walking legs are large and serve as formidable weapons. Smaller 

 pincers are present on the next two pairs of walking legs, but are 

 lacking on the last two pairs. The exopodite is never present. 



A pair of mouth parts is present on each of the segments vii, viii, 

 and ix. These appendages are known respectively as the first, 

 second, and third maxillipeds. Each of these has a basal 

 protopodite, composed of the coxopodite and basipodite, and also 

 a gill-bearing epipodite, noted above. The epipodite of the first 

 maxilliped, however, lacks the gill filaments. The third maxilliped 

 on segment ix is the largest. In this appendage, the exopodite is 

 comparatively short, and consists of a basal portion bearing a 

 flexible, filamentous structure. The endopodite is much larger 

 than the exopodite and is composed of five joints, the general 

 structure being somewhat like the endopodite of the walking legs, 

 except that a pincer is not present. The first and second maxilli- 

 peds are smaller than the third maxilliped, but their structure is 



