CRUSTACKAXS IX ( 1 1. 1 . I ( !' I K RTS TU5KS. IO5 



the female Polyonyx had left the tube and was on the surface of 

 the sand. The other three crustaceans stayed within until 

 July 27, at about 8.00 p. m., when the male Polymyx emerged. 

 The water in the jar at that time was murky, but did not have a 

 very bad odor. On the morning of July 29 the water had some 

 odor; the Polyonyces were dead on top of the sand and the 

 PinnixcE had left the tube but were alive and active. 



The crabs in experiment 2 were the largest obtainable and the 

 apertures at the ends of the tube tips were of medium size. 

 They seemed to have little difficulty in passing in or out, though 

 one would not think so at first glance. Pinnixa walked in 

 sideways; Polyonyx extended its chelse and one of them pre- 

 ceded the body, the other followed. 



Locomotion outside the tubes was first studied in a large flat 

 dish containing sea water. Pinnixa did not use its last leg when 

 walking forward, but when going sideways used all the walking 



4 



FIG. i. Diagrams to represent the method of locomotion used by Polyonyx when 

 resting on its setal fringe with its body against some object. 



legs, except the chelipeds, which were hugged close against the 

 body; it was never seen to move backward. Polyonyx usually 

 moved backward when in the open and sideways along the sides 

 of the dish. In the latter situation it always faced toward the 

 center of the dish, or, if in haste, stood with its ventral surface 

 against the side of the dish and walked along on the tips of its 

 chelipeds and the bristles along their outer edges (Fig. i). It 

 very much hurried an animal sometimes turned on its back and 

 flapped its abdomen, thus swimming slowly. \Yhen placed in a 

 vertical glass tube filled with sea water Polyonyx kept from 

 falling by bracing the fringe of bristles on the chelipeds and the 

 second and third walking legs forward; the fourth leg serving as 

 a prop behind (Fig. 7). The small fifth leg was not used. Loco- 

 motion was always sideways. In a similar situation Pinnixa 

 braced with all its walking legs; the first and second were ex- 

 tended forward, the third below, and the fourth and fifth 



