194 



CRUSTACEA. 



splits into two distal branches, the inner being, as a rule, called the 

 inner branch, or endopodite (Fig. 90, en), and the outer the outer 

 branch, or exoj)odite (ex). While the exopodite and the endopodite 

 undergo considerable variation, developing as lamellate appendages 

 or adopting some altogether different form, or breaking up into a 

 very varying number of separate joints, the protopodite is in most- 

 cases composed of two joints (Figs. 90, 91, 1, 2). The first of these 

 joints (the proximal joint) (1) was called the basal joint by Claus, 

 and the coxopodite by Huxley, while the second (the distal joint) {2) 

 is known as the stem-jomt (Glaus) or hasipodite (Huxley). It should 

 be mentioned that in many cases (especially in the Malacostraca), 

 the joints of the endopodite seem to form a direct continuation of 



Fig. 91. — Three Crustacean limbs (after Claus). A, maxilla of Calanella. B, thoracic limb of 

 Nehalia. C, first maxillipede of an advanced Pencteus larva. 1, first, 2, second joint of the 

 protopodite ; k, masticatory processes of the same ; en, endopodite ; e.r, exopodite ; ej), 

 epipodial plate ; ep', rudiment of a branchial tube. 



the protopodite (Fig. 91 B), while the exopodite appears like a 

 lateral appendage. This condition cannot, however, be regarded 

 as primitive. 



The close proximity of the ventrally placed Crustacean limbs 

 allows mutual inter-action of the two members of one and the same 

 pair, and we therefore often find, on the inner side of the endopodite 

 and protopodite, processes of very various kinds which act mechani- 

 cally upon any foreign bodies (particles of food) that may come 

 between the two approximated limbs. Such processes have received 

 the general name of endites, but when found on the protopodite they 

 may bear more special names (Fig. 91, Ic), being known as masticatory 



