ECHINODEKMA. 
107 
Fig. 1. 
O 
A. Anchor and plate of Synapta. B, C. Tables of Holothuria impatiens ; and 
D. Holothuria atra : from various aspects. E. Spicule from sucker of 
Stichopus variegatus, magnified about 200 times. 
Fi<?. 2. 
Diagram of Water-vessels. 
c.c. Circular canal, with p.v, its Polian vesicles; from it a radial canal (v.c.y_iB 
given off along the lower surface of each arm; this supplies, by side 
branches, the suckers, s ; connected with each sucker is a contractile 
swelling or ampulla (a). The circular canal is in connection with the 
exterior by s.c, the stone-canal, and opens to it by the madreporite (m). 
