THE HOLOTHURIDEA. 



471 



Fig. 136.— Synapta diqitata and inh wrens (After Baur.) * 



A, larva wirh the bilateral ciliated band, and wheel-shaped calcareous plates: 

 ventral view. a. mouth and gullet; b, stomach; c, intestine and anus; d, sacs 

 of the enteroeoele (sausage-shaped bodies) at tbe sides of the stomach; ^rudi- 

 ment of the ambulacra! vascular system. B, further advanced condition of the 

 larva in which the oral aperture is obsolete (the so-called " pupa-stage 1 '), and the 

 cilia are arranged in zones, i, tentacnla ; k, Polian vesicle ; /, the longitudinal 

 muscles of the body-wall. C, a young Synapta, in which the ciliated zones have 

 disappeared ; with its five tentacles and the wheel-shaped calcareous bodies at 

 its hinder end. m, the madreporic canal which now opens into the cavity of the 

 body. D. a young Synapta inhwrevs with anchor-shaped calcareous spicula, ex- 

 cept at the hinder end of the body, where they are small and polygonal. E, lon- 



1 "Beitrage zur Naturgeschichte der Synapta dig/itala." ("Nova Acta," 

 xxxi., 1864.) 



