1^07] Jennings. — Behavior of the Starfish. 151 



various methods to escape, taking much time and making many 

 movements of the most varied character before they were finally 

 successful. According to Preyer, when the experiment is re- 

 peated several times on the same individual, the time required for 

 escape becomes less, and the number of useless motions performed 

 is likewise decreased. The starfish has thus improved through 

 experience; it might be said to have "learned" how to escape; or 

 it has formed the habit of escaping in a certain way. But Preyer 

 gives no precise data on this matter, as to the time or the number 

 of movements used ; his statement is evidently based merely on a 

 general impression. As we shall soon see, later work has not 

 substantiated these results, in the case of starfish left to work out 

 for themselves a method of action. 



Preyer (/. c.) described certain other experiments, on the 

 brittle star, the results of which were of such a character that 

 Preyer characterized the starfish as "intelligent." These ex- 

 periments are of much interest in themselves, and they formed 

 the basis for the later work of Glaser (1907), immediately to be 

 mentioned. It will, therefore, be worth while to take them up 

 briefly, the more so since Preyer 's results have been called in 

 question by Loeb. It will be of interest further to determine 

 just what were Preyer 's grounds for attributing intelligence to 

 the brittle-star. Preyer slipped a short rubber tube over one of 

 the rays of the animals to its base. He found that this caused 

 the creature to perform many varied movements till by one of 

 them the tube was removed". Among the methods described by 

 Preyer for removing the tube, there are certain ones which look 

 like a definite attempt toward accomplishing this end. Thus, 

 the animal, after dragging behind it for a time the arm bearing 

 the tube, stopped, placed another arm against the tube, and 

 pushed it ofit", the spines along the sides of the arm serving to 

 give it a hold on the tube. Sometimes one of the adjacent arms 

 was used in this way, sometimes two. In another case, where 

 the tube covered the stump of an arm, the animal placed this 

 stump bearing the tube against the side of the disk and strongly 

 rubbed. This displaced the tube a little, but it still remained 



" Preyer 's experiments were performed on species of Ophiomyxa and 

 Ophioderma, from the Bay of Naples. 



