14 EMBRYOLOGICAL MONOGRAPHS. 
14/-19. Amphiura squamata. From Hubert Ludwig, Zur Entwickelungsgeschicte des Ophiurenskelettes, 1882 
(Morphol. Studien, II., Heft 2). Zeits. f. Wiss. Zool., XXXVI., Pl. XI. 
A,, Ay. First and second ambulacral plates. Ra. Radials of the young ophiuran. 
A d,, Ady, Ads, ete. First, second, third, ete. ad- TT Terminal plates. 
ambulacral plates. To. Torus angularis. 
C. _ Dorsocentral plate. t. Teeth. 
m. Madreporic plate. V V7, Ventral plates. e 
0. Oral plates (mouth shields). a Remnant of embryonic skeleton. 
f. Primary radials. 
14’. Young Amphiura, seen from the dorsal side. The composition of the plates, of y-shaped rods, is still plainly 
visible. 
15. Somewhat older stage, seen from the actinal side. V, oldest yentral plate ; V7, very young ventral plate ; 
f, rudimentary teeth. 
16. Somewhat older than fig. 14/, but younger than fig. 15, seen from the dorsal side. 
17. Somewhat older than the stage corresponding to fig. 19, seen from the dorsal side, showing the arrangement 
of the intermediate plates formed between the central and the primary radials. 
18. Somewhat older than the stage of fig. 17, seen from the dorsal side ; the intermediate plates have greatly in- 
creased in size and number. 
18’, Shows the arrangement of the plates of the actinal side in a stage slightly older than fig. 17. 
19. Stage corresponding to fig. 15, seen from the dorsal side ; intermediate plates begin to appear between the 
central plates and the primary radials, 
20-23. Ophiopholis (?) and Amphiura (2). From Alexander Agassiz, On the Embryology of Echinoderms. Mem. 
Am. Acad., [X:, figs. 29, 31-33, 1864. 
20. Ophiopholis bellis? From a drawing made wnder the direction of L. Agassiz in 1849. Abactinal view of a 
young Ophiopholis to show the arrangement of the plates of the disk. 
21-23. Amphiura ? 
21. A full-grown Pluteus, in which the water-tubes, 2, w!, are plainly seen. d, digestive cavity ; m, mouth ; 
a, anus; ¢, rudimentary tentacular lobes of the water-system; v!, anal, and v, oral vibratile cord; 
e!-et, arms of the Pluteus. 
22. Older stage, seen from the abactinal side, in which the arms of the Pluteus (e'/-c+) are almost entirely resorbed ; 
the two long arms ¢! are still intact, they are omitted for want of space. 7, abactinal region ; y, rudi- 
mentary terminal plate ; y/, adambulaecral plate ; 74, junction of limestone rods of the long arms ¢’. 
23. The same, seen from the actinal side ; lettering as above : s, actinal region ; ¢, /, tentacular loops. 
24, 25. Ophiocoma rosula. From T. H. Stewart, On the Young State of Ophiocoma rosula, and on the Form and 
Development of the Spines of this Species. Ann. & Mag. Nat. Hist., XVIII., 1856, Pl. XV. 
24. Young Ophiocoma seen from the abactinal side. 
25. Actinal view of central portion of the disk. 
26-31. Amphiura squamata. From Max Schultze, Ueber die Entwickelung von Ophiolepis squamata, einer leben- 
diggebahrenden Ophiure. Archiv. f. Anat. Phys. u. Wiss. Med., 1852, Pl. I. 
26. Ovarian eggs of Amphiura squamata. 
27. Young embryo with rudimentary provisional limestone rods. 
28. Somewhat older than fig. 27, the embryonic limestone rods are arranged symmetrically. 
29. Older embryo. In addition to the provisional limestone rods, a, we have also the radials, b, developed ; and 
the first trace of the terminal plates, c. 
30. The embryo has assumed a pentagonal outline ; of the provisional limestone rods we find only the remnants at 
a; lettering as before ; the plates of the abactinal side are seen through from the ventral side under the 
rudimentary actinal plates. 
31. Portion of a young Amphiura measuring }/”’ in diameter, seen from the actinal side: @, interbrachial dorsal 
plates ; bc, actinal plates adjoining actinostome ; d d, interbrachial plates of the actinal side ;. ¢ e, spoon- 
shaped brachial plates; f, terminal plates; g, g, tentacles ; h, teeth. 
32, 33. Viviparous Ophiuran. From August Krohn, Ueber einen neuen Entwickelungsmodus der Ophiuren. 
Archiv. f. Anat. Phys. u. Wiss. Med., 1857, Pl. XIV. B. 
32, Actinal view of ophiuran embryo ; a, pentagonal disk of young ophiuran; }, central cavity, the future 
mouth ; ¢, tentacles ; d, tentacles of actinostome ; ¢, remnant of rudimentary Pluteus. 
33. Young ophiuran of same embryo; a, dorsal plates ; 4, arm plates ; c, terminal plate ; d, spines of the actinal 
side projecting beyond the disk. 
