ECHINODERMATA 



211 



6. Reproduction sexual; development usually indirect, *.>., 

 with a metamorphosis. Reproduction by budding does not 

 occur. 



243. General Survey. The majority of echinoderms have 

 a central disc in which is located portions of the various sets 

 of organs. Ordinarily there radiate from this disc more or less 

 clearly defined rays or arms in which lie radial outgrowths from 



FIG. 97. 



FIG. 97. Starfish, from chart of Leuckart and Nitsche. 



Questions on the figure. How would you describe the symmetry of the animal ? 

 Identify and name, by comparison with the diagrams and the text, all the struc- 

 tures which show in the figure. Compare this with specimens or figures of the 

 common American species and note the chief differences. 



certain central organs. The spaces between the rays (inter- 

 radii) may be bridged by growth in such a way that the distinc- 

 tion between rays and disc is not marked (echinoids) . In crinoids 

 the arms may be much branched. The oral-aboral axis is usu- 

 ally pronounced, often short, and is vertical in position (aster- 



