LIGHT REACTIONS AND PHOTOTAXIS 599 



negative, they were removed from the glasses with a pipette. 

 As a consequence, the tubes in the violet and the green light 

 were first emptied, all nauphi having become negative; the blue 

 and the yellow tubes followed much later, and the red would 

 take a very long time. 



Similar results were obtained with color-filters. The same 

 glass tubes which had been disposed in the spectrum were put 

 into wider glasses containing a colored liquid. The glass tubes 

 were corked and entirely surrounded by the liquid. The filter- 

 liquids consisted for 



Violet of methyl-violet (area transmitted from 400-470/x and from 640-700m) 



Blue of copperacetate + methyl-violet with addition of ammonia (area trans- 

 mitted from 445-485/i) 



Green of copperacetate + potassium monochromate with addition of ammonia 

 (area transmitted from 480-560/x) 



Red of lithium carmine (area transmitted from 610-700/i) 



The layer of colored liquid surrounding the glasses was no- 

 where less than 12 mm. deep. The transmitted areas were 

 tested with a Zeiss spectroscope and as far as possible the extinc- 

 tion of all the areas was made equal by means of the Engelmann 

 'Microspectralphotometer;' that is to say: each area was made 

 to transmit the same fraction of the colored light of equal wave 

 lengths existing in the solar spectrum by regulating the satura- 

 tion of the colored solution. 



As in the previous experiments, the different position of the 

 animals in each color after distribution in the different glasses 

 was very noticeable; as usual the nauplii were nearest the bottom 

 in the green, nearest the surface in red and violet. If the sensi- 

 tiveness of the larvae stood in a favorable proportion to the 

 intensity of illumination, it was frequently observed, that they 

 became negative in the violet and green only and remained 

 positive for several hours in all other colors. If I then brought 

 the glasses into full sunhght, the animals became negative also 

 in the blue and finally in the red light. Brought back into 

 diffused daylight they became positive in the reverse order. 

 The experiments with color-filters are, however, not as conclu- 

 sive as the others, owing to the impossibility of separating with 



