124 CATALOGUE OF THE ECHINODERMATA OF 



pedicellariae upon certain starfishes, whilst species closely allied 

 possess these organs : these without pedicellariae have precisely 

 similar habits, and doubtless live upon the same food. This 

 may be exemplified in Asterias violacea and Solaster papposa, 

 both of which are found upon our rocks. The former is abun- 

 dantly supplied with these organs, the latter is entirely without 

 them. Forbes, in his "History of British Starfishes," makes 

 frequent allusions to the feeding of these animals : in many 

 cases, animals of considerable magnitude have been observed to 

 be their food.* We must therefore, I think, seek for the func- 

 tions of these organisms in a different direction ; for with the 

 evidence which can readily be adduced relative to the food of 

 starfishes and urchins, it is unsatisfactory to assume they feed 

 upon beings which no one can prove to be their prey. In the 

 case of the Spatangidce, however, there must be a reservation, 

 not with reference to pedicellariae assisting in procuring food, 

 but as to the food itself, for they undoubtedly imbibe an immense 

 number of minute animals, possibly including infusoria. It is 

 probable, however, that rhizopods form the principal part of their 

 food, a Spatangus from Shetland (in the possession of the Rev. 

 A. M. Norman) having been found to contain an incredible num- 

 ber of the shells of these animals, and when we remember they 

 are both found on the same kind of bottom, this is easily ac- 

 counted for. With these facts before us we cannot, I think, re- 

 gard the pedicellariae as a sort of " avicularia," but may they 

 not very properly be regarded as a modified form of tentacles ? 

 Sensitive as they are in the highest degree, they may be so 

 many " organs of touch," performing in the urchin (where they 

 appear to attain their highest development) somewhat similar 

 functions to the "pinnated cirrhi" of the Ophiuroidea, and, in 

 a minor degree, similar duties amongst the Asteroidea, disappear- 

 ing altogether in the Holothnroidea. But, with this theory, we 

 have still to account for their absence in certain genera of the 

 Asteroidea ; for example, Solaster, Porania, and Cribrella. 



The classification and nomenclature employed in the following 



* See Hist. Brit. Starfishes, pp. 86, 88, 134, &c. 



