EMBEYOLOGICAL M0:N"0GKAP1I.S, 



PLATE xrir. 



Development of Holothuroidea. Figures from Johannes Mulleu and Elias Metschnikoff. 



1-11. Synapta {Auricularia with calcareous wheels). 



1 3 4. From Joliaiiiics Miiller, Ueber die Larven uml die Metamoi-pliosc der Ecliiuodertnen, Zweite Abhandlung, 



1848, PI. IV. Abliaudl. d. K. Akad. d. Wiss. Berlin, 1849. 



2 5-11. From .loliainu'S Miiller, Ueber die Lai-ven und die Metanior[iliosen der Holothurien iiiid Asterien 



(Ft. 3), (1849-50,) Pis. I., II., III. Abhaudl. d. K. Akad. d. Wiss. Berlin, 1850. 



d". Passage of vibratile cord from the oral to the dorsal cord. 

 Anus. 



Dorsal pore. 



Tentacular rosette of the water system. 

 Tentacular lobes of the water system. 

 Calcareous wheel. 



1. Young Auricularia, seen from the ventral side. 



2. Somewhat older Auricularia, seen from the ventral side. 



3. Older stage, in which the arms are developed. 



4. Somewhat older Auricularia ; the tentacular lobes of the water system, i, are well seen. 



5. About in the same stage as the preceding, seen obliquely from the dorsal side. 



6. Auricularia at the time of the metamorphosis ; the lateral arras have disappeared, and broad transverse 



bands of vibratile cilia have been formed. 



7-11. Stjnapta, continued. 



Digestive cavity. /. 



Anal opening. g- 



Circular ring of the water system. h. 



Polian vesicle. i. 



The five branches of the circular ring leading to k. 



the tentacles. /. 



Vesicles (otoliths) with gi-anules round the oral iii. 



water-ring. n. 



Tentacular chamber. 



Canal with the crescent-shaped limestone arc. 

 Lateral muscular bands. 

 Calcareous gland at the anal extremity. 

 Cavity in which the tentacles are developed. 

 y rods of the or"al calcareous ring. 

 Intestine. 



Position of the cavity where the tentacles 

 eventually break through. 



e. Calcareous skeleton of the oral ring. 



7. Synapta pupa, somewhat compressed, and somewhat older than the preceding stage. 



8. Synapta pnpa, somewhat more advanced than the preceiiing stage. 



9. Young creeping Synapta. 



10. Young Synnpta, .somewhat compressed. 



11. Young Synapta, still older, compressed. 



In figs. 9-1 1 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, continvM. From Elias Metschnikoff, Studien iibcr die Entwickelung der Echinodermen und 

 Nemertincn, 1869, Pis. I., II. Mem. Acad. Imp. de St. Petersbourg, VIPSer., XIV., No. 8. 



c. Cutis. 



ce. Oisoph.agus. 



c d. Cavity of the lateral disk. 



d'. Left water-tube. 



dr. Eight water- tube. 



p a. Dorsal pore. 



s. Stomach. 



s c. Outer layer of the lateral disks. 

 si. Inner layer of the lateral disks. 

 <!-<*. First to fifth tentacular lobes of the oral 

 ring of tentacles. 



V a. Original pouch of the water system. 



V I. Otoliths round the oral water-ring. 



