ECHIKODEKMATA. 67 



branches, each of which, just at the issuing out from the 

 body, divides itself into two, and each of the ten branches 

 thus formed, does again divide into two parts, making 

 twenty lesser branches, and each of these doth again 

 divide, making in all forty. These again divide into eighty, 

 and these into 160, and they again into 320. The division 

 is again repeated, making 640, afterwards 1,280, 5,120, 

 10,240, 20,480, 40,960, and at the fourteenth division^ 

 beyond which the farther expansion could not be distinctly 

 traced, there were 81,920 small tendrils or threads in 

 which the branches of this Star-fish terminate." 



We next arrive at a group called 



Snake-tailed Star-fishes (Of&itiridae),* one of which is 

 represented at Fig. 44, 4. The rays are no longer divided 

 into branches, but are, nevertheless, curiously constructed, 

 and being twisted about with great activity when the 

 creature is disturbed, look not a little like the tails of 

 serpents whence the name given to this family. 



A very interesting circumstance in the economy of 

 these animals is their extreme brittleness, whence they 

 have merited the name of "Brittle-Stars" On the least 



FlG. 45. BRITTLE STAR. 



alarm or excitement, the creature throws off one or per- 

 haps all its rays, and breaks them into fragments. This 

 * o<i?, ophis, a snake ; ovpa, oura, the tail, 



