PLATE XIII. 



[All the figures excepting 8, which is taken from Ludwig, '82, and has par- 

 ticular reference to AsteHna gibbosa, are o{ Pycnopodia helianthoides.'\ 

 Figs, i and 2. A young individual, aboral and oral views respectively, in the 

 S-rayed stage, with rays Ix and rx very small. 

 3 and 4. Outline tracings of an individual. Oral and aboral views re- 

 spectively, in the 12-rajed stage, Ix^ and rx^ barely visible from the 

 aboral side. 

 Fig. 5. An oral view of an interradius, in which a new ray with three pairs of 

 visible tube feet and several pairs yet concealed in the pocket, is in 

 course of development. At this stage nothing of the new ray can be 

 seen from the aboral side. 



6. The aboral disc, seen from the inside, and as though looked down 

 upon, showing the apical radial muscle bands, the madreporite, and 

 the position of the anus close to the origin of the muscle of ray A. 



7. The peristomeal region, seen from the inside of the animal and looked 

 down upon, showing the racemose gland, r.g., and the stone canal, 

 S.C., and their relation to the rays which are indicated by the skeletal 

 plates belonging to both radii and interradii. 



8. Diagram of metamorphosing young of Asterina gibbosa, copied from 

 Ludwig, '82, p. 173. Compare with fig. 4. 



(272) 



