40) EMBRYOLOGICAL MONOGRAPHS. 
31. Young Holothuria, about in the stage of fig. 30; the vibratile cilia have disappeared, and the young Holothu- 
rian now creeps by means of its tentacles and ambulacral sucker. 
82. Young Holothuria, somewhat older, under compression, seen from the dorsal side. The cireular oral canal, 
the stone canal, the Polian vesicle, and the ventral ambulacral canal, are well seen. 
33-37. Auricularia with dendritic and calcareous gland. 
33-35, 37. From Johannes Miiller, Ueber die Larven und die Metamorphose der Holothurien und Asterien (Pt. 3), 
1849-50, Pl. V. Quoted above. 
36. From Johannes Miiller, Ueber die Larven und die Metamorphose der Echinodermen, Vierte Abhandlung, 
1850-51, Pl. I. Quoted above. 
33, 34. Two successive stages of the pupa, under compression. 
35. Holothurian larva of the same, with free tentacles. a, digestive cavity ; ¢, circular canal; c!, Polian vesicle ; 
cl, the five branches of the circular oral canal leading to the tentacle ; ¢, caleareous oral ring ; 7, tentacles ; 
g. stone canal, with its caleareous ring ; 4, the lateral elastic spheres ; //, the odd terminal anal sphere ; 
i, the terminal anal dendritic gland ; %, the remnants of the vibratile cord ; 7, transverse bands of vibra- 
tile cilia. 
36. Somewhat more advanced young Holothuria, with a small ventral ambulacral sucker : the vibratile cilia of the 
transverse bands have disappeared. d, the tentacular-like bodies at the base of the oral tentacles along the 
calcareous ring ; f, circular canal; f’, Polian vesicle ; g, stone canal and its calcareous ring ; 0, extremity 
of the ventral ambulacral canal. 
37. Young Holothuria, in a stage intermediate between figs. 35 and 36. 
