244 MANUAL OF ELEMENTARY ZOOLOGY 



absent altogether. The first two pairs are sensory, and have 

 long lashes for searching the surroundings of the animal. 

 The next six pairs are jaws, used for bringing the food to 

 the mouth and chewing it : these are short and stand close 

 behind the mouth. Then come two great shears or pincers 

 which are the principal grasping organs, next four pairs of 

 legs, and then the six pairs of limbs of the abdomen, of 

 which some are concerned in reproduction, some help the 

 animal forward by paddling while it is walking, and the last 

 pair are used in rapid swimming. Exopodites are wanting 

 from the legs, great pincers, and first two pairs of jaws, and 

 epipodites are found only upon the limbs of the thorax. 



The first limb of each side is known as the antennule or 

 first antenna. It is peculiar in having three, instead of 

 two, joints in its protopodite. The first joint 1 is large and 

 three-sided: upon its upper side there opens, by a slit 

 edged with bristles, the statocyst, which will be described 

 later. The third joint bears two many-jointed lashes' or 

 flagella. These are often compared to the exopodites and 

 endopodites of the other limbs, but it is not certain that 

 the comparison is justifiable. The outer lash bears on the 

 under side of most of its joints certain peculiar bristles 

 which are supposed to serve the sense of smell. The 

 second limb is the antenna (or second antenna). Its coxo- 

 podite is short and wide and bears below a knob, upon 

 which opens the green gland or kidney. The basipodite 

 is divided lengthwise into two pieces. The exopodite is a 

 fiat, triangular, pointed scale, and the endopodite is a very 

 long flagellum. The third limb or mandible has a large, 

 broad, and very strong coxopodite 2 with a toothed incisor 

 edge which bites against that of its fellow on the other side 

 of the body. Above the incisor edge, and therefore hidden 



1 See the following note. 



2 Perhaps really a joint known as the precoxa, which corresponds to 

 the first joint of the antennule and is in the raaxillule separated from 

 the basipodite by a small basal piece representing the coxopodite. 

 There is reason to believe that the so-called coxopodite of the mandible 

 is a precoxa, the true coxopodite being absent. In the second maxilla 

 the precoxa may be represented by the first lobe of the protopodite, 

 and in the thorax the precoxa of each limb is absorbed into the side of 

 the body. There is no evidence as to its identity in the abdominal 

 limbs. 



