516 
HUBERT LYMAN CLARK 
LITERATURE CITED 
Agassiz, a. 1909 Amer. Jour. Sci., vol. 28, pp. 490-492; pi. 2. 
Becher, S. 1907 Zeit. f. w. ZooL, Bd. 88, pp. 545-689; pis. 32-36. 
1908 Die Stammesgeschichte der Seewalzen, pp. 1-88. 
1910 Zool. Jahrb. Anat. Bd. 29, pp. 315-366; pis. 20-24. 
Clark, H. L. 1898 Mem. Boston Soc. Nat. Hist., vol. 5, pp. 53-88; pis. 11-15. 
1908 The Apodous Holothurians, pp. 1-231; pis. 1-15. 
CuENOT, L. 1891 Arch. Biol., T. 2, pp. 313-680; pis. 24r-31. 
Edwards, C. L. 1909 Jour. Morph., vol. 20, pp. 211-230; pis. 1-3. 
Grave, C. 1902 Johns Hopkins Univ. Circ, no. 157, pp. 57-59. 
LuDwiG, H. 1881 Arch. Biol., T. 2, pp. 41-58; pi. 3. 
1891 Sitz. Kon. Preuss. Ak. Wiss. Berlin, Heft 2, pp. 85-98. Also in 
Ann. Mag. Nat. Hist. (6), vol. 8, pp. 413-427. 
1892 Zeit. f. w. Zool., Bd. 54, pp. 350-364; pi. 16. 
1898 Holothurien: in Ergebnisse d. Hamburger Magalhaensische 
Sammelreise, 98 pp. and 3 pis. 
MacBride. E. W. 1903 Phil. Trans. B., vol. 195, pp. 285-327; pis. 7-16. 
Ostergren, H. 1907 Zur Phylogenie und Sytematik der Seewalzen: in Zoolo- 
giska Studier tillagnade Professor T. Tullberg, pp. 191-215. 
Pourtale.s, L. F. 1851 Proc. Amer. Ass. Adv. Sci., Fifth meeting, pp. 8-16. 
Semon, R. 1888 Jenaische Zeit. Naturw., Bd. 22, pp. 175-309; pis. 6- 12. 
Theel, H. 1877 Nov. Act. Reg. Soc. Sci., Ser. 3, vol. extraord. 17, pp. 1-18) 
pis. 1-2. 
PLATE 1 
explanation of figures 
1 Old gastrula of Chiridota. X 70. ar = archenteron; hi = blastopore; hy-en 
= hydro-enterocoel. 
2 Young larva of Chiridota. X 70. ac = anterior coelom; nr = archenteron; 
hi = blastopore; cb = ciliated bands; cp = calcareous particles; hy = hydrocoel; 
I en = left enterocoel; r en = right enterocoel; ivp = water-pore. The hj^drocoel 
already shows the five primary outgrowths and even the secondary ones are indi- 
cated. 
3 Very young pcntactula of Chiridota. X 70. a c = anterior coelom; al = 
alimentary canal; be = coelom, cb = ciliated bands; c p = calcareous particles; 
h t = primary tentacles; p v = polian vessel; wp = water-pore. 
4 Pentactula of Chiridota. X 70. a = anus; a c = anterior coelom; at c — 
atrial collar; ch = ciliated bands; c p = calcareous particles; cr = calcareous 
ring; i = intestine ;;? f = primary tentacles; = polian vessel; rn = radial nerve; 
so = sense-organ; st = stomach. 
5 Figures showing the development of the trochoderma-like ^'heels (/) from 
the simple discs (a). X 310. 
