MEM. M. C. Z., IX. No. 2, —ECHINODERMATA. 39 
12, A very young Auricularia, with yellow pigment spots. This figure is not a younger stage of the following 
ones, which all belong to Synapta. 
13. Young Auricularia, in which the water system pouch and the lateral disks have not yet appeared. 
14, Older Auricularia, in which the original problematic body has divided into two, forming the two lateral disks. 
15. The lateral disks have now assumed their characteristic appearance, and the water system has become five- 
lobed. 
16. Somewhat more advanced Auricularia ; the water system shows a secondary set of smaller lobes between the 
larger ones, and has taken a horseshoe shape ; the lateral disks have increased in size. 
17. Shows the horseshoe-shaped water system, with a portion of the left water-tube. 
Figs. 13-17 correspond to the period included between the stages figured by Miiller. See above, figs. 1-3. 
18. Auricularia with calcareous gland. From Johannes Miller, Ueber die Larven und die Metamorphose der 
Holothurien und Asterien (Pt. 3), 1849-50, Pl. IV. Quoted above. 
18. Auricularia, seen from the ventral side. @, mouth ; 6, cesophagus ; ¢, digestive cavity ; d, intestine ; ¢, anus ; 
f, caleareous gland ; g, gray granulation covering f. 
19. Auricularia with eleven spheres. From Johannes Miiller (Pt. 3), Pl. IV. Quoted above. 
19. Adult Auricularia, seen from the oral side. a, mouth; 6. esophagus ; ¢, stomach ; ¢, problematic body 
(lateral disk) ; g, depression in which the mouth is placed. 
20-32. Auricularia with elastic spheres. 
20-22, 29. From Johannes Miiller, Ueber die Larven und die Metamorphose der Echinodermen, Vierte Abhand- 
lung, 1850-51, Pl. I. Abhand. d. K. Akad. d. Wiss. Berlin, 1852. - 
93-28, 30-32. From Johannes Miiller, Ueber den Allgemeinen Plan in der Entwickelung der Echinodermen (Pt. 
6), 1852, Pls. I1I., V., VI. Abhand. d. K. Akad. d. Wiss. Berlin, 1853. 
20-21. Auricularie in the stage of development preceding the cylindrical form. 20 is seen from the dorsal side, 
21 from the ventral side. 
a. Mouth. f. Lobes of the oral tentacular system. 
b. (Esophagus. g. Caleareous ring of dorsal pore. 
c. Stomach. h. Water system. 
c’. Intestine. h!. The eleven elastic spheres. 
d. Vibratile cord. i. Caleareous gland. 
e. Problematic bodies. o, Anus. 
92, Auricularia somewhat younger than the preceding stages, at the time when the caleareous ring of the dorsal 
pore begins to form. 
a. Mouth. az. Part of the bilateral vibratile cord, which 
6. (Césophagus. disappears. 
c. Digestive cavity. I, II, III, 1V, V. Portions of the bilateral vibratile 
d. Intestine. cord, which become the first to fifth trans- 
e. Anus. verse ciliated bands. 
f. Tentacular system. 3!, 4. Lobes of the dorsal part of the bilateral 
g- Caleareous ring of the future madreporic vibratile cord, which become part of the 
opening. third and fourth transverse ciliated band 
o. Caleareous sphere. on the dorsal side. 
23. Fully developed larva, of which the mouth and cesophagus can still be seen. The bilateral vibratile cord is 
in process of passing into the transverse ciliated band. 
24. A pupa without a mouth, seen obliquely from the ventral side ; on the ventral side only can the anterior part 
of the bilateral vibratile cord be recognized ; the posterior transverse ciliated bands are fully formed. 
25. Another pupa without a mouth, seen from the dorsal side ; the transverse ciliated bands are not yet all 
closed ; the first and second are not yet complete. 
. A pupa shortly before the oral tentacles force their way through ; 1/, dorsal part of the first vibratile cord, I. 
A pupa, still pelagic ; the tentacles have just forced their way through the anterior extremity. 
. Somewhat older pupa, in which the membrane uniting the tentacles and connecting with the perisome is 
developed. 
29, Young Holothuria, in which, besides the transverse ciliated bands, traces of the bilateral ciliated cord can 
still be seen. 
. Young Holothuria, with a ventral sucker, under compression, seen in profile, showing the yentral ambulacral 
canal and its vesicle connecting the sucker with the circular canal. 
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