THE HOLOTHURIDEA. 



471 



Fig. 1S6.—Sj/napta digit a ta and inhcerens (After Baur.) 1 



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

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

 of the enteroccele (sausasre-shaoed 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 larva in which the oral aperture is obsolete (the so-called "pupa-stage"), and the 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 : A\ Polian vesicle ; /. the longitudinal 

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

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

 its binder end m, the madrenoric canal which now opens into the cavity of the 

 body. D. a voun^ 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 "Beitriige zur Naturgeschichte der Synapta digitata." ("Nova Acta," 

 xxxi., 1864.) 



