STARFISHES 65 



specimen. As it does not generally break up before it is raised 

 above the surface of the sea, cautiously and anxiously I sank my 

 bucket to a level with the dredge's mouth, and proceeded in the 

 most gentle manner to introduce Luidia to the purer element. 

 Whether the cold air was too much for him, or the sight of the 

 bucket too terrific, I know not, but in a moment he proceeded 

 to dissolve his corporation, and at every mesh of the dredge 

 his fragments were seen escaping. In despair, I grasped at the 

 largest, and brought up the extremity of an arm with its termi- 

 nating eye, the spinous eyelid of which opened and closed with 

 something exceedingly like a wink of derision." 



The second class of the Echinozoa comprises the Sand and 

 Brittle Stars, creatures with disk-like bodies and long, slender 

 rays, or arms, and the scientific name of the class, Ophiuroidea, 1 

 which literally signifies " snake-tail," not only expresses the 

 dominating feature of their organisation, but also describes the 

 writhing, snake-like movements of the long, slender arms by which 

 the animals move along and climb over the rocks. The long, 

 snaky arms of the Brittle Stars are attached to a small and usually 

 rounded body-disk, to which the viscera are confined. The top 

 and sides of the body-disk generally bear various sized plates, 

 more or less covered with granules, spinelets, or groups of spines. 

 In different species, the precise manner in which the plates on 

 top of the body-disk are arranged varies, but five pairs of plates, 

 called the radial shields, are always present, though not always 

 clearly visible. Each pair corresponds to the base of one of the 

 rays, one plate lying on either side of the ray, near the edge of 

 the body-disk. This is usually, but not always, notched for the 

 arm-bases, that dovetail, as it were, into the disk, and are visible 

 on its under side, separated from one another by groups of regu- 

 larly arranged plates, which converge towards the central mouth. 

 Each arm-base is separated from the plated interradial areas at its 

 sides by slitlike openings, which are usually single, occasionally 

 double. They are called the genital slits, and lead into thin- 

 walled pouches at the sides of the rays, and apparently have a 

 double function, serving as respiratory organs, and for the re- 

 ception of the ripe ova, which may be either at once discharged, 



1 The name of this class is derived from three Greek words : ophis, snake ; oura, 

 ail ; and eidos, form. 



