322 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



were localized in any particular organs, as we had 

 found to be the case with the sense of sight, I first 

 tried the effect of removing the five ocelli. This 

 produced no difference in the result of the above 

 experiment witli hungry Star-fish, and therefore I 

 next tried the effect of cutting oft* the tips of the 

 rays. The Star-fish behaving as before, I then pro- 

 gressively truncated the rays, and thus eventually 

 found that the olfactory sense was etjually dis- 

 tributed throughout their length. The question, 

 however, still remained whether it was equally dis- 

 tributed over both the upper and the lower sufifaces. 

 I therefore tried the eff"ect of varnishing the upper 

 surface. The Star-fish continued to find its food as 

 before, wdiich showed that the sense of smell was 

 distributed along the lower surface. I could not try 

 the converse experiment of varnishing this surface, 

 because I should thereby have hindered the action 

 of the ambulacral feet. But by another method 

 I was able nearly as well to show that the upper 

 surface does not participate in smelling. This 

 method consisted in placing a piece of shell-fish 

 upon the upper surface and allowing it to rest there. 

 When this was done, the Star-fish made no attempt 

 to remove the morsel of food by brushing it off" with 

 the tips of its rays, as is the habit of the animal 

 when any irritating substance is ^^pj^lied to this 

 surface. Therefore I conclude that the upper or 

 dorsal surface of a Star-fish takes no part in minis- 

 tering to the sense of smell, which by the experi- 

 inent of varnishing this sui-face, and also by that 

 of progressively truncating the rays, is proved to 



