324 



COMPARATIVE ANATOMY 

 C. The Respiratory Organs Gills. 



CHAP. 



Respiration always takes place in Crustaceans by means of the 

 outer integument. In small Crustaceans, in which the cuticle lying 

 over the hypodermis is thin and delicate, the whole body surface 



Fio. 225. Pleopoda (abdominal feet) of Leptostraca and Malacostraca. A, End of the 

 abdomen of Diastylis stygia (after G. O. Sars) ; V, VI, VII, abdominal segments ; VII, telson ; p$, 

 pleopoda of the 6th segment ; en, endopodite ; ex, exopodite. B, 2d pleopod with gills, exo- and 

 endo-podite of Siriella Thompson!! (after G. 0. Sars). C, End of the abdomen (caudal fin) of Siri- 

 ella gracilis (after G. O. Sars) ; VI, 6th abdominal segment ; VII, 7th abdominal segment (telson) ; 

 en, ex, endo- and exo-podites of the 6th pleopoda, which together with the telson form the caudal" 

 fin ; g, auditory organ. D, An anterior pleopod of Nebalia (after Glaus) ; ex, exopodite ; en, 

 endopodite. E, Nebalia, 6th pleopod of the 9 (after Glaus). F, Anilocra (Isopod), caudal tin ; VI, 

 6th abdominal segment ; VII, telson ; p 6 , 6th pleopod with exopodite (ex) and endopodite (en) (after 

 Delage). G, Lysianassa producta (Amphipod) ; end of the abdomen with the 4th, 5th, and 6th 

 pleopoda, p, p 5 , p$ ; IV, V, VI, VII, abdominal segments ; en, endo-, ex, exo-podite (after Goes). 

 //, Diastylis stygia, 1st pair of pleopoda ; ex, exo-, en, endo-podite (after G. O. Sars). " I-N, 

 Astacus fluviatilis. I, 3d pleopod of male ; K, 1st pleopod of female ; L, 1st pleopod of male ; 

 M, 3d pleopod of the female; N, 2d pleopod of the male. 1, Anterior surface ; 2, posterior 

 surface ; ex, exopodite ; a, the rolled-up plate of the endopodite ; 6, jointed end of the endopodite 

 (after Huxley). 



breathes. This is especially the case in Ostracoda, Copepoda, many 



Cladocera, and many Cirripedia, which have no specific respiratory organs. 



In the great majority of Crustaceans, however, the respiration 



is particularly active at definite parts of the body, even if in addi- 



