ie ECHINODERMA. 
GENERAL PART. 
The chief Divisions of the Echinoderma. 
ECHINODERMA. 
Centroniz, Pallas, Misc. Zool. (1766) p. 153 f.n. 
Echinodermes, Cuv. Tab. Elem. (1798) p. 643. 
Radiaires echinodermes, Lamhk. Syst. ae s. Vert. (1801) p. 343. 
Kchinoderma, Latreille, Ham. Anim. (1825) p. 582; Lfeffer, Verh. 
Ver. Hamb. vi. (1887) p. 107. 
Kchinodermata, Fleming, Brit, An. (1828) p. 472; Forbes, Brit. 
Starf. (1840) p. xi; Gray, Syn. Brit. Mus. (1840) p- 58; 2d. Brit. 
Rad. 1848, p. 1; Haeckel, Gen. Morph. ii. (1866) p. 1xii; atque auct. 
complur. 
Cyclozoa echinoderma (pars), Eichw. Zool. Spec. i. (1829) p. 222. 
Echinodermaires, de Bi. Dict. Sci. Nat. lx. (1830) p. 169. 
Enteractinozoa, Bronn, Kl. u. Ordn. (1860) p oie 
Annuloida (pars), Hucley, Class. Anim. (1869) p. 127. 
The Echinoderma are Metazoa Coelomata, 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 
ccelom 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 CysTipEa (?). 
* For the reasons for this arrangement of the classes, ¢f. Aun. & Mag. N. H. 
1891, viii. p. 206. 
