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 with hungry Star-fish, and therefore I 
next tried the effect of cutting off 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 equally dis- 
tributed throughout their length. The question, 
however, still remained whether it was equally dis- 
tributed over both the upper and the lower surfaces. 
I therefore tried the effect of varnishing the upper 
surface. The Star-fish continued to find its food as 
before, which 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 applied 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- 
ment of varnishing this surface, and also by that 
of progressively truncating the rays, is proved to 
