36 



A. M. REESE 



was surrounded except at one end by a black cloth, and the 

 whole apparatus was operated in a photographic dark room. 

 Observations were made at intervals of five minutes. The tem- 

 perature varied from 16.5° C. to 19° C. Eleven animals were 

 used. At the beginning of the experiment the animals . were 

 quiet and equally distributed through the aquarium. 



TABLE IV 



Observations 1 2 3 4 5 6 7 8 9 10 11 12 13 



Facing light 7 10 9 7 10 10 8 10 9 7 8 8 4 



S-A-A-aAA a A A A A A A- 



Facingdark 1124113124337 



S S .. S- A- S S- S S- S- S- S A- 



In light end 787788 10 876954 



S-A-A aA aA a a a a a A- 



In dark end 4344331345267 



S S- A- S- A- S- S S S- S- S S A- 



Observations 14 15 16 17 18 19 20 21 22 23 24 25 26 



Facing light 6 9 10 7 10 8 8 9 10 8 11 9 9 



A- A A A A A A a A A A- A- A- 



Facingdark 32.. 2132213022 



A- A- .. S- S S S S .. S- .. S S 



In light end 5 7 6 7 6 8 8 9 6 4 7 9 8 



A-AA aAAA a a aAA a 



In dark end 6454533257423 



A- A A- A- S- S A S- S- S- S- S- S 



Observations 27 28 29 30 31 32 33 34 35 36 37 Totals 



Facing light 88878987554 298 



A A A A- S S- A- A- A A A- 



Facingdark 13243.. 34662 90 



S S S S S .. S S S-A-A- 



In light end 97974444534 244 



a a A A- A A A- A A- A- A 



In dark end 24247777687 163 



SSSSSSSSS-AA 



For explanation of letters see page 32. 



Observations 1 to 12 were made at night; the other observa- 

 tions during the morning and afternoon of the following day. 

 Between observations 22 and 23 was an interval of two hours 

 and five minutes during which the tungsten light was shining 

 into the end of the aquarium. After observations 9 and 25 all 

 the animals were gently pushed into the end of the aquarium 

 away from the light. After observation 12 and about one hour 

 before observation 13 the animals were fed as much raw meat 

 as they would eat. It will be seen from table IV that the aver- 

 age activity of the animals facing the light was greater than 



