THE HOLOTHURIDEA. 



471 



Fig. 136.— Synapta diaitata and inharens. (After Baur.) l 



A, larva with 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 the sides of the stomach ; e, 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 larva in which the oral aperture is obsolete (the so-called " pupa-stage "), and the 

 cilia are arranged in zones, i, tentacula; k, Polian vesicle ; I, 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 madrenoric canal which now opens into the cavity of the 

 body. D. a young Synapta inhcerens 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 digritata." ("Nova Acta," 

 xxxi., 1864.) 



