DEVELOPMENT OF THE YOUNG ASTERIAS. 213 



suckers begin to be apparent under the form of 

 globular protuberances, disposed in ten concentric 

 rows (PI. IV. fig. 3, djf). If in this condition the 

 little being is detached from the spot where it has 

 fixed itself, it is still able to swim about in the sur- 

 rounding water by means of its ciliated surface, always 

 keeping the organs of attachment directed forwards ; 

 but if left undisturbed, it remains perfectly still and 

 motionless, presenting what M. Sars calls the crinoid 

 state of development, considering that in this con- 

 dition it corresponds to the state of the fixed Encrinite. 

 At this stage, the body of the young Star-fish may 

 still be said to be bilateral ; for in all its movements 

 the organs of attachment are directed forwards, and 

 both sides of the body correspond exactly to each 

 other ; but by degrees this bilateral condition is con- 

 verted into the radiated form that characterizes the 

 third or perfect state of the Asterias ; the body begins 

 to assume a pentagonal outline, from the angles of 

 which, short, blunt rays begin to project (PL IV. 

 fig. 3, g), and the tentacula, now presenting the form 

 of retractile cylinders, and completely furnished with 

 their terminal suckers, become efficient instruments 

 of locomotion. The red spots, regarded as the eyes^ 

 are visible at the extremities of the nascent rays ; 

 the mouth shows itself in the centre of the ventral 

 aspect of the body, and numerous spines make their 

 appearance. Lastly, the apparatus for attachment 

 begins to diminish in size, and soon completely 

 disappears ; so that the young Asterias, having at- 

 tained its perfect form, is ready to enter upon the 

 duties of its station. 



