120 



NATURAL HISTORY. [CH. VII. 



that my curiosity was excited to observe them 

 more minutely ; and, as the creature was not at nil 



timid, I could easily observe it through a glass of 

 some power. The caudal instrument, I discovered 

 by this means, consists of a double row of white 

 cartilaginous rays, {b) disposed in a circle, one row 



With the rays open, With the rays shut, 



within the other, and what was most singular, thcvse 

 were retractile in a curious manner, to the horns of 

 the snail. The rays were united by a soft, moist, 

 gelatinous membrane, but so as to be individually 



