MEM. M. C. Z., IX. No. 2. — ECHINODEEMATA. 



39 



12. A' very young .\uricularia, with yellow pigment spots. This figure is not a j'ounger stage of the following 



ones, which all belong tn Synapta. 



13. Youn" Aurieulavia, in which the water system pouch and the lateral disks have not yet appeared. 



14. Older Auricularia, in which the original ]iroblematic 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 ,\uricularia ; the water system shows a secondary set of smaller lobes between the 



larc'er ones, and has taken a horseshoe shape ; the lateral disks have hicreased 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 icifh calcareous ghmul. From Johannes Miillcr, Ueber die Larven und die Metamorphose der 



Holothurien und Asterien (Tt. 3), 1849-50, PI. IV. Quoted above. 



18. Auricularia, seen from the ventral side, a, mouth ; b, oesophagus ; c, digestive cavity ; d, intestine ; c, anus ; 



/, calcareous gland ; f/, gray granulation covering/. 



19. Auricula/ria with eleven qihercs. From Johannes Miiller (Ft. 3), PI. IV. Quoted above. 



19. Adult Auricularia, seen from the oral side, a, mouth ; 6. oesophagus ; c, stomach ; c, problematic body 



(lateral disk) ; y, depression in which the mouth is placed. 



20- 

 23- 

 20- 



20-32. Atiricularia with clastic sj)hc7xs, 



■22, 29. From Johannes Miiller, Ueber die Larven und die Metamorphose der Echinodennen, Vierte Abhand- 

 lung, 1850-51, Fl. I. Abhand. d. K. Akad. d. Wiss. Berlin, 1852. 



■28, 30-32. From Johannes Miiller, Ueber den AUgemeinen Plan in der Entwiekelung der Echinodermen (Ft. 



6), 1852, Pis. III., v., VI. Abhand. d. K. Akad. d. Wiss. Berlin, 1853. 

 •21. Auricularise in the stage of devehipment preceding the cylindrical form. 20 is seen from the dorsal side, 

 21 from the ventral side. 



/. Lobes of the oral tentacular system. 



g. Calcareous ring of dorsal pore. 



h. Water system. 



hi. The eleven elastic spheres. 



i. Calcareous gland. 



0. Anus. 



22. 



the future madreporic 



23. 

 24. 



26. 

 27. 

 28. 



29. 



30, 



a. Mouth. 



b. (Esophagus. 



c. Stomach. 

 c'. Intestine. 

 cl. Vibratile cord. 

 e. Problematic bodies. 



Auricularia somewhat younger than the preceding stages, at the time when the calcareous ring of the dorsal 

 pore begins to form. 



X. Part of the bilateral vibratile cord, which 

 disappears. 



I, II, III, IV, V. Portions of the bilateral vibratile 

 cord, which become the first to fifth trans- 

 verse ciliated bands. 



3', 4'. Lobes of the dorsal part of the bilateral 

 vibratile cord, which become part of the 

 third anil fourth transverse ciliated band 

 on the dorsal side. 



Fully developed larva, of which the mouth and resophagus can still be seen. The bilateral vibi'atile cord is 



in process of passing into the transverse ciliated band. 

 A pupa without a mouth, seen obliquely from the ventral side ; on the ventral side oidy can the anterior part 



of the bilateral vibratile cord lie recognized ; the posterior transverse ciliated Viands are fully formed. 

 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. 

 Young Holothuria, in which, besides the transverse ciliated bands, traces of the bilateral ciliated cord can 



still be seen. 

 \'oung Holothuria, with a ventral sucker, under compression, seen in profile, showing the ventral ambulacral 



canal and its vesicle connecting the sucker with the circular canal. 



