434 PROCEEDINGS OF THE AMERICAN ACADEMY. 



further asserts that the animals are incapable of burrowing with the 

 tail first. Miiller ('41, p. 399), however, in his description of the ani- 

 mal's habits implies that it enters the sand tail first, and often burrows 

 only far enough to cover the main portion of the trunk, leaving the 

 anterior end exposed. I attempted to ascertain the truth of the matter 

 by carefully uncovering animals that had buried themselves, thus 

 determining by direct inspection which end had probably entered 

 the sand first. I also noted in instances where the animal had failed 

 to cover itself completely which end was left exposed. These instances 

 were more conclusive than those of completely covered animals, for in 

 these cases there was no chance for an unobserved reversal of ends as 

 might occur where the animals were for a short time out of sight. In 

 the great majority of these cases the animals had evidently entered the 

 sand tail first, though there were some instances, especially among the 

 imperfectly covered ones, in which it was clear that they had entered 

 with the anterior end first. Other evidence on this question was de- 

 rived from animals on which a slight operation had been performed. 

 Amphioxus from which a part of the tail had been removed entered 

 the sand only after many trials, whereas others whose rostrum had 

 been cut off but whose tail was intact seemed to have no difficulty in 

 making their way into the sand. These observations are in agreement 

 with what was noticed in animals that had partly or completely buried 

 themselves, and I am therefore convinced, notwithstanding Steiner's 

 statement to the contrary, that amphioxus usually enters the sand tail 

 foremost. 



In one respect the amphioxus buried in the sand were very different 

 from those lying freely on the surface. The free individuals were 

 usually very straight, as though held in form by the stiffness of the not- 

 ochord. The buried individuals, on the other hand, had when in the 

 sand a very tortuous outline, as though they had crowded their way in 

 between the coarse pieces of shell and coral. Such individuals imme- 

 diately became straight on being released from the sand. 



Rheotropism, though present, is not a prominent feature in the re- 

 actions of amphioxus. In the inlet at the small landing pier in front of 

 Hotel Frascati large schools of small fish could be seen definitely ori- 

 ented in reference to the swift current. These schools maintained a 

 more or less constant position by swimming against the current about 

 as rapidly as the current would have carried them in the opposite 

 direction. When living amphioxus were dropped into these schools, 

 they drifted among the small fish on the way to the bottom without as 

 a rule the least locomotor movement, and, when they did move, they 

 never showed any tendency to orient to the current. Moreover, when 



