12 



ECHIXODERMA. 



GENERAL PART. 

 The chief Divisions of the Echinoderma. 



ECHINODERMA. 



Centronix, Pallas, Misc. Zool. (1766) p. 153 f.n. 



Echinodermes, Car. Tab. Elim. (1798) p. 643. 



Badiaires echinodermes, Lamk. Syst. An. s. Vert. (1801) p. 343. 



Echinoderma, Latreille, Fain. Anim. (1825) p. 532; Pfeffer, Verh. 



Vet: Hamb. vi. (1887) p. 107. 

 Echinodermata, Fleming, Brit. An. (1828) p. 472 ; Forbes, Brit. 



Star/. (1840) p. xi ; Gray, Syn. Brit. Mm. (1840) p. 58 ; id. Brit. 



Bad. 1848, p. 1 ; Haeckel, Gen. Morph. ii. (1866) p. lxii ; atque auct. 



coniplur. 

 Cyclozoa echinoderma (pars), Eichio. Zool. Spec. i. (1829) p. 222. 

 Echinodermaires, de Bl. Diet. Sci. Nat. lx. (1830) p. 169. 

 Enteractinozoa, Bronn, Kl. u. Ordn. (1860) p. 421. 

 Annuloida (pars), Huxley, Class. Anim. (1869) p. 127. 



The Echinoderma are Metazoa Ccelomata, in which bilateral 

 symmetry is early or altogether lost, but may be secondarily 

 acquired ; it is generally replaced by a quinqueradial disposition of 

 nearly all the parts. The integument and some of the internal 

 organs are strengthened by a crystalline deposit of carbonate of 

 lime, mesodermal in origin, plexiform in structure; this may 

 remain microscopic and spicular, or part may form macroscopic rods 

 or plates and give rise to a continuous skeleton. A section of the 

 coelom becomes modified into a special system of sacs, canals, and 

 tubes, which form the water-vascular system, and have an ambula- 

 tory or respiratory function or both. The sexes are generally 

 separate, and development is rarely direct. 



They are ordinarily marine in habit, but a few live in brackish 

 water, and they have had representatives in every age in which 

 animals are known to have existed. 



Tabular View of the Classes of Echinoderma *. 



Branch A. INCALICULATA. 

 Stage a. Anactinogonidiata. 



Class 1. HoLOTHURIOIDEA. 



Branch B. CALICULATA. 



Stage a. Anactinogonidiata. 



Class 2. Some Cystidea (?). 



* For the reasons for this arrangement of the classes, cf. Ann. & Mag. N. H 

 1891, viii. p. 20b\ 



