18 



SVEN LOVEN, ECHINOLOGICA. 



soliition of continuity intervened between this circle and tlie 

 next, the plates of whioh, the second ones and the following, 

 M^ere oomprehended in the fixed portion of the corona. The 

 third, fourth and fifth, when completed, were regnlarly hexa- 

 gonal, and higher than they were broad; the second, the lowest 

 pair, was, as yet alone, somewhat defornied and depressed. It 

 was preparing to separate from the following-, to descend and 

 to begin forming the flexible continnation of the corona, the 

 meinbrana bnccalis . The colnnins of the anibnlacra will 

 grow rapidly, nevv plates will form continnally at their abo- 



Buocal i)art of an aiiibulaenun in Cidaris papillata. 



ral terminations, and by virtne of the vis a tergo bronght 

 on by their angmenting nnmber and enlargement, and the re- 

 sistance afForded by the radial of the calyx, the plates will 

 come to change their places relatively to the interradials, and 

 glide gradnally downward between these. towards the stomal 

 region. Whenever. in this manner, one of a pair of plates 

 attains tlie limit of the fixed part of the corona, the solution 

 of continnit}^ is repeated, the snture which marks its adhesion 

 to the next following plate is seen to open, and the plate to 

 be set free, and to pass, as if discharged thr(^ngh the outlet 



