252 Papers from the Marine Biological Laboratory at Tortugas. 



In any given problem, the successful solution of which depends upon random 

 activity, the animal which has the greatest activity is likely to show a shorter 

 time record for the early trials. 



In the second place, the curve for the noddy drops to a minimum at the 

 fourteenth trial, which is maintained almost uniformly for the rest of the 

 tests. The variation occurring throughout the curve for the sooty has already 

 been remarked upon. A comparison of the two curves from the fourteenth 



15 

 14 

 13 

 12 

 II 

 10 

 in 9 



I 2 3 4- 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 



Trials 



Fig. 4. — Curves showing average time of three noddies in leaving Porter's simple maze. 



trial on brings out what I consider the second great difference between the 

 tw^o species : The sooty is highly excitable and nervous ; the noddy is stolid 

 and indifferent. The sooty, even though going through habitual reactions, 

 is disturbed by slight changes in intra and extra-organic stimulations; the 

 noddy on the other hand is indiff'erent to slight changes in stimulation. 



While these conclusions are based, it is true, upon few records, I feel 

 after much observation of the birds that the amassing of a larger number 

 of statistics would establish even more firmlv the conclusions sfiven above. 



EXPERIMENTS WITH THE MAZE IN FAINT ILLUMINATION AND IN 



TOTAL(?) DARKNESS. 



The trained animals used in the above experiment were tested at night 

 with the maze faintly illuminated. The situation was as follows : For two 

 or three days I had accustomed the birds to a late night feeding. I then 

 made the room in which the maze was kept completely dark by boarding 

 up the windows. I next mounted a commercial candle of ordinary size 

 (standard candles were not available) upon a glass plate. I then suspended 

 the candle so mounted over the center of the maze at a height of 50 cm. 

 I found it absolutely impossible under these conditions to avoid shadows 



