inversion of the primitive sarcode layer which seems to corres- 

 pond to the ectoderm. 



Within a few hours or sometimes days, there- are indications of 

 the calcareous areolated plates forming the cup of the future cri- 

 noid. Soon others appear forming a sort of trellis work of plates 

 and gradually build up the stalk, and lastly appears the cribriform 

 basal plate. Fig. 86, B, c, represents the young crinoid in the 

 middle of the larva, whose body is somewhat compressed under the 

 covering glass. Next appears a hollow sheath of parallel calca- 

 reous rods, bound, as it were, in the centre by the calcareous 

 plates. This stalk (B, c) arises on one side of the digestive 



Fig. SB. 



cavity of the larva, and there is no connection between the body 

 cavity of the larva and that of the embryo crinoid. 



Two or three days after the appearance of the plates of the 

 crinoid, the larva begins to change its form. The mouth and di- 

 gestive cavity disappear, not being converted into those of the 

 crinoid. The larva sinks to the bottom resting on a seaweed or 

 stone to which it finally adheres. The Pentacrinus is embedded in 

 the former larval body (the cilia having disappeared), now consti- 

 tuting a layer of sarcode conforming to the outline of the Antedon. 



Meanwhile the cup of the crinoid has been forming. It then 

 assumes the shape of an open bell ; the mouth is formed, and five 

 lobes arise from the edges of the calyx. Afterwards five or more, 

 usually fifteen tentacles, grow out, and the young Antedon appears 



