58 EMBRYOLOGICAL MONOGRAPHS. 
Pa ACIME XT Te 
Development of HotorHuroweEa. Figures from JOHANNES MULLER and Evias MerscuniKorr. 
1-11. Synapta (Auricularia with calcareous wheels). 
1, 3, 4. From Johannes Miller, Ueber die Larven und die Metamorphose der Echinodermen, Zweite Abhandlung, 
1848, Pl. IV. Abhandl. d. K. Akad. d. Wiss. Berlin, 1849. 
2, 5-11. From Johannes Miiller, Ueber die Larven und die Metamorphosen der Holothurien und Asterien 
(Pt. 3), (1849-50,) Pls. L., IL., IJ. Abhandl. d. K. Akad. d. Wiss. Berlin, 1850. 
a. Mouth. d@', Passage of vibratile cord from the oral to the dorsal cord. 
b. (Esophagus. e. Anus. 
c. Digestive cavity. Dorsal pore. 
c!. Intestine. Tentacular rosette of the water system. 
d. Dorsal part of the simple vibratile cord. Tentacular lobes of the water system. 
d', Oral part of the vibratile cord. Caleareous wheel. 
Sh oS 
. Young Auricularia, seen from the ventral side. 
. Somewhat older Auricularia, seen from the ventral side. 
. Older stage, in which the arms are developed. 
Somewhat older Auricularia ; the tentacular lobes of the water system, 7, are well seen. 
. About in the same stage as the preceding, seen obliquely from the dorsal side. 
. Auricularia at the time of the metamorphosis ; the lateral arms have disappeared, and broad transverse 
bands of vibratile cilia have been formed. 
a orem OD 
7-11. Synapta, continued. 
a. Digestive cavity. jf. Tentacular chamber. 
b. Anal opening. g. Canal with the crescent-shaped limestone are. 
c. Circular ring of the water system. h. Lateral muscular bands. 
c!. Polian vesicle. i. Caleareous gland at the anal extremity. 
c!!, The five branches of the circular ring leading to k. Cavity in which the tentacles are developed. 
the tentacles. 7. y rods of the oral calcareous ring. 
d. Vesicles (otoliths) with granules round the oral m. Intestine. 
water-ring. n. Position of the cavity where the tentacles 
e. Caleareous skeleton of the oral ring. eventually break through. 
7. Synapta pupa, somewhat compressed, and somewhat older than the preceding stage. 
8. Synapta pupa, somewhat more advanced than the preceding stage. 
9. Young creeping Synapta. 
10. Young Synapta, somewhat compressed. 
11. Young Synapta, still older, compressed. 
In figs. 9-11 the tentacles of the young Synapta have forced their way through the actinal extremity of the 
pupa, and the broad transverse bands of vibratile cilia disappear with advancing development. 
12-17. Synapta, continued. From Elias Metschnikoff, Studien iiber die Entwickelung der Echinodermen und 
Nemertinen, 1869, Pls. I., Il. Mém. Acad. Imp. de St. Pétersbourg, VII¢ Sér., XIV., No. 8. 
c Cutis. se. Outer layer of the lateral disks. 
ec. (Esophagus. st. Inner layer of the lateral disks. 
ed, Cavity of the lateral disk. “-t4, First to fifth tentacular lobes of the oral 
d’/, Left water-tube. ring of tentacles. 
dr. Right water-tube. va. Original pouch of the water system. 
pa. Dorsal pore. vi, Otoliths round the oral water-ring. 
s. Stomach. 
