GENERAL STRUCTURE OF STELLERIDA. 



465 



on the lower surface only, and in the central line of each ray, 

 that we find the ambulacral plates. The tubular feet are very 



FIG. 708. ASTERIAS, OR STAR-FISH. 



numerous, though short, in the Star-fish ; but much fewer in 

 some other forms belonging to the Order. They are connected, 

 as in the Echinus, with a tubular apparatus, which enables the 

 animal to project them either together or separately. The ovaria 

 are disposed in a radiated form around the mouth ; and they are 

 found to be turgid in the spring and the commencement of 'the 

 summer. 



1 104. In the Star-fishes the development usually takes place 

 in a manner very similar to that already described for the Echi- 

 nida ( 1101). The eggs are not extruded at once and left to 

 their fate, but the parent retains them for a considerable time in 

 a cavity which is generally formed by drawing up the disc and 

 the bases of the arms ; and it is said that when the ova have 

 been removed from this shelter, and placed at some distance 

 from the parent, the latter has been seen to move directly to- 



