PLATE XIV. 



Pycnopodia helianthoides. 



Fig. 9. An interradial diagrammatic section, reconstructed from many actual 

 sections, of a young ray with three pairs of tube feet. 



10. A frontal section of an interradius with new ray developing, corre- 

 sponding about to the line a b, fig. 9. The pocket of the new ray in- 

 dicated in dotted outline, r.p. 



II and 12. Two frontal sections of a young ray showing details of the 

 growing parts and the tissue in which they are embedded. Fig. 11 

 corresponds about to line cd, fig. 9, though the development is some- 

 what more advanced than the ray shown in this latter. Fig. 1 1 is at 

 a slightly higher level than 12. 



13. An interradial vertical section showing, with other things, the prob- 

 able initial step in the beginning of a new ray. This consists in 

 the incipient evagination on the water ring canal, w.r.c, of the 

 radial water canal, r.w.c' . This fig. should be compared with fig. 9. 



(274) 



