POTERIOCRINlDvE PENTACRINDS 113 



pieces are also cennected laterally by the intervening plated membrane. 



The ten secondary rays are each composed of several joints generally varying I'rom 

 three to four, five or six, but the number is not constant even in the same specimen. 

 Miller, with much apparent justness, considered these irregularities as designed for a 

 desired end, namely — That as the cuneiform articulations never afford support to a ten- 

 taculum the vacuity occasioned by tiieir absence would render their net-like expansion 

 less complete, unless some compensating contrivance was resorted to. This end is 

 accomplished by the number of joints below the bifurcations varying in the diflferent 

 rays, so that a tentaculated articulation in one ray is placed opposite to a plain cuneiform 

 joint of the adjoining ray, and by this means the vacancy can if required be swept 

 by the tentaculum opposite to it. 



Other bifurcations take place until the total number of the lesser rays appear to amount 

 to one hundred and twenty ; but it is difficult to estimate their number correctly, as the 

 specimens brought to Europe are generally more or less imperfect, for owing to the 

 shrinking or destruction of the connecting ligaments the ray articulations become sepa- 

 rated, and in endeavouring to repair the injury, attention is not always directed to original 

 structure. 



It has been supposed that the sexual organs of crinoids are placed in the arms, but 

 this question is still involved in much obscurity, and we are of opinion that in some 

 genera the ovarial organs will be fouud to occupy a position in the dorsal side of the cup; 

 while in others they may be ventral, or situated where the rays are given off", or as is 

 now believed, in the rays themselves. Our knowledge on this subject even among 

 existing echinoderms is far from complete, and when we attempt an anatomical inves- 

 tigation of animals whose existence was so remote, our difficulties increase a hundredfold, 

 for the numerous and varied forms of extinct crinoids may have been modelled, not upon 

 one, but upon several laws of organic developement. — Even in the recent P. Caput 

 Meduscp we believe the ovarial orifice has not been discovered, and we freely admit that 

 it has baffled all our researches. 



Miller, at page 54 of his work on the Crinoidea, mentions that the specimen he exa- 

 mined, had suffered considerable mutilation previously to its removal from the sea 

 bottom, and that by its power of reproduction, two secondary rays, with their minor 

 divisions had been constructed to supply the place of the lost ones. This we are 

 informed is a mistake, and that tiie supposed reproduction was merely a restoration 

 with gum, some of the intervening joints having being lost in its transit from tiie 

 West Indies. 



By these remarks we do not intend to question the correctness of the opinion as to 

 the power of reproduction possessed by these animals, for we have undoubted examples 



p 



