310 



COMPARATIVE ANATOMY 



CHAP. 



A q 



the 3 other joints together with the flagellum to the endopodite, and the scale 

 to the exopodite, of a typical biramose limb. This is clear from the fact that the 2d 

 antennae of the Malacostracan larva? (Nauplius, Protozocea) show the typical biramose 

 .structure, the exopodite (which is often still jointed) being transformed in the course 

 of development into the squame of the antenna in the adult. The 3 distal joints of 

 the shaft are thus only the 3 proximal joints of the endopodite enlarged. 



Arthrostraca. Amphipoda, the squame (exopodite) is wanting. In the female 

 Ifi/pcridce the antennae are rudimentary. Isopoda, squame wanting. In Sopyridce 

 and Entoniscidce the antennae rudimentary. Anisojwda, squame present in Ajtscudcs. 





FIG. 210. Second or posterior antennae of various Crustaceans. A, lolanthe acanthonotus, 

 l.>pod (after Beddard). J7, Eulimnadia texana, larva (after Packard). C, Cyclops signatus 

 (after Uljanin). D, Pseudocalanus elongatus (after Brady). E, Trebius caudatus, parasitic 

 i. nwod (after Kroyer). F, Eulimnadia Agassizii, adult Phyllopoil (after Packard). G-I, 

 Euphausia pellucida (after Sars). G, Last Fiircllia stage ; H, first Cyrtopia stage ; I, young Euph- 

 ansia. K, Astacus fluviatilis (after Huxley); go, aperture of the green gland (antennal gland) ; 

 ex, I'xopodite (squame); en, endopodite with flagellum ; /, proximal; II, distal joint of the proto- 

 podite. 



Thoracostraca. Cumacea, antennae without squame, in the male with unusu- 

 ally long flagellum, in the female rudimentary. Stomatopoda, with large squame. 

 Schieopoda, with well -developed squame (Fig. 210, G-I). Decapoda, except the 

 Brachyum, with squame (Fig. 210, K), the outer being the posterior antennae. 



The antennal glands which have been observed both in the Entomostraca and the 

 Malacostraca show a constant relation to the 2d antennae. That is to say, they 

 always open on the basal joint of their protopodites. 



c. The Mandibles (Fig. 211). 



The mandibles correspond with the 3d pair of extremities (the 2d 

 pair of biramose feet) of the Nauplius. They lie to the front at 

 the side of the mouth and serve for mastication. They are origin- 





