XI 



PHYLUM ARTHROPODA 



501 



plate (ep) having a plume-like gill (g) attached to it. Obviously 

 such an appendage is biramous, but with one of its branches 

 greatly in excess of the other : the first two segments of the axis 

 (pr. 1, pr. #) form the protopodite, its remaining five segments 

 (en. 1-5) the endopoclite, and the feeler, which is directed out- 

 wards, or away from the median plane, the exopodite (ex). The 

 folded plate (ep) is called the epipodite : in the natural position 



5. E". d Maxilla 6. I^Maxilliped 



\-},r2 



Stffi* 1 



Q.Copulafory Organs lO.Swimmmg Poor 



ll.Uropod 



FIG. 397. Typical appendages of Astacus. en. 1 ", poclomeres of endopoclite; cp. epipodite ; 

 ,' . I'xopodite ; fl. flagella ; </. gill ; pt: 1, p>: -2, podomeres of protopodite ; 1 3, podomeres of 

 axis of antennule. (After Huxley.) 



of the parts it is directed upwards, and lies in the gill-cavity 

 between the proper wall of the thorax and the gill-cover (Fig. 404). 

 Its position is thus very similar to that of the flabellum of Apus, 

 while the gill attached to it is comparable to the bract. 



The five legs (S) differ from the third maxilliped in their greater 

 size, and in having no exopodite : in the fifth or last the epipodite 

 also is absent. The first three of them have undergone a curious 



