336 



W. C. ALLEE 



Fig. 8 Rheotaxis during isopod development in different amounts of oxygen. 

 >Si, Stream isopods in high oxygen, So, in low oxygen; Pi, pond isopods in high 

 oxygen, P2, in low oxygen. 



1 — I — I — 1 — I I I I I — I I r 1 I — r— 1 — r— I — I — ] — I — I — r 



J_J I I 1 1 I I I I 1 I I I I I I I l__l I I L 



Days 1 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 21 22 23 24 



Fig. 9 The effect of depressing agents upon rheotaxis. A, low temperature; 

 B, chloretone 1/200 per cent solution; C, carbon dioxide, 200-300 cc. per liter; 

 D, KCN, n/100,000; E, Starvation. 



