4 



THE AMERICAN NATURALIST 



[Vol. XLI 



The time occupied by the fish in entering the holothurian was 

 not taken, but in my notes which I made immediately after my 

 observations, I find that I estimated the time to be probably not 

 more than half a minute. 



In order to give some of the workers in the laboratory, who had 

 not seen all of the events described above, an opportunity to view 

 this interesting instance of animal behavior, the experiment was 

 repeated. 



When the finger-bowl had been removed from the holothurian 

 a second time the fish was found to be again in the water. 



Then were repeated in minutest detail the actions which I have 

 described above. The fish swam actively at the surface of the 

 water — part of the time with its mouth above the surface. Then it 

 began to move in a more or less aimless fashion. Finally it touched 

 the holothurian with its nose, this time about the middle of the 

 length. Then followed in exact order the reactions which liad 

 been observed before, viz., the rapid bumping of its nose against 

 the side of the holothurian, the undeviating progress towards the 

 posterior end, the whip-like motion and insertion of the tail while 

 the nose was still in contact with tiie margin of the cloacal aperture, 

 the leisurely straightening of the body, and the gradual retreat into 

 the resisting, at least not assisting, holothurian. 



It should be added that tiie above account is made up from 

 notes which I wrote rlown immediately after the observations were 

 made. Except in one of two details they are confirmed by Dr. 

 Ulric Dahlgren who has kindly placed his notes at my disposal. 



The above accomu is the story of the way one Fierasfer gained 

 entrance to its host. Whether every individual Fierasfer would 

 behave exactly tiie same, under similar circumstances, perhaps 



I am indebted to Professor Cornelia M. (lapj) for reference to 

 an excellent article on the habits, anatomy, etc., of Fierasfer by 

 Dr. Carlo Emery, i Fauna uml Flora ,1rs c'nljrs mn Xraprl, vol. 1, 

 ISSO). J)r. Kmerv note> that Fi(M-asfer enters it> host tail first. 



A somewhat similar habit i> indi<-at..l for the counnon eel l.v 

 xvhat the veteran and accurate obs<M-ver, \ inal X. Mdwards, tells 

 me, r/^., that eels go into holes tail first. 



