1889-90-] On the EcJiinoidea or Sea-UrcJiins. 349 



pedicellarite are given. These authorities assert their main 

 function to be that of laying hold of pieces of sea- weed, in order 

 to aid progression while the animal is climbing perpendicular 

 or inclined rock-surfaces. This assertion is fortified by the 

 result of many experiments, and other observers have since 

 confirmed its truth. The blades or mandibles of the pedicel- 

 larife are exceedingly sensitive, the slightest touch on the 

 interior surface of any one blade causing the whole mechanism 

 to close instantly. They vary considerably in shape, different 

 forms being found even on the same animal. In the third 

 volume of the " Challenger Eeports," — the ' Report on the 

 Echinoidea,' by Prof. A. Agassiz, — numerous forms are figured. 

 The largest of the pedicellarise on the sea-urchins are about 

 one-eighth of an inch in length. What seems to be but a 

 modified form of the pedicellari^e is found on the Spatangideee. 

 These bodies have been named " clavulse," and are " minute 

 spines with expanded head and a calcareous pedicel covered 

 by ciliated epithelium, attached to minute tubercles which 

 form regular bands known as fasdoles or semitce." ^ 



The other curious appendages of the " test " of a sea-urchin 

 are the sphaBridia, or sj^Mrides, — so called by Prof. Loven, 

 who has issued a beautiful quarto on the Echinoidea, in which, 

 various forms of spheeridia are figured. They are minute glob- 

 ular bodies, said to be covered with cilia, and mounted, like the 

 pedicellariai, on long stalks. Sphaeridia are found on all living 

 sea-urchins except the genus Cidaris, and yet it is only very 

 lately that they were noticed at all. What their function is 

 has not yet been absolutely determined, though Prof. Lov^n 

 conjectures them to be organs of taste. He bases this sup- 

 position on their being found in greatest numbers around the 

 oral aperture. Prof. Loven says : " Disposes, comme ils le 

 sont, d'une maniere constante, aux approches de la bouche et 

 le plus souvent k la base des grands tentacules buccaux, on 

 est done conduit a leur supposer la fonction de faire connaitre 

 la nature des substances que I'eau ambiante tient en solution, 

 et de servir, de cette maniere, a guider I'animal dans la 

 recherche de sa nourriture. lis meritent bien, avec tant 

 d'autres points de I'organisation des Echinoidees, d'etre Studies 



^ ' Forms of Animal Life,' by G, Rolleston and W. H. Jackson, second edition 



(1888), p. 558. 



