652 



F. W. (lAMRLK AND F. W. KERBLE. 



Table. 



VI 



Name of 

 experiment. 



Light- 

 intensity 

 experiment 2 



VII 



VIII 



IX 



XI 



Coloured 



light 

 experiment 



Constant 

 iUumination 

 experiment 



Constant 

 dark experi- 

 ment 1 



Constant 



dark 



experiment 2 



Experiment 

 with blinded 

 H i ]) p o 1 y t e 



Object of 

 experiment. 



To test effects of 

 different light- 

 intensities 

 compared witli 

 tliat of exposure 

 to red, green, 

 and blue light 

 on the diurnal 

 and nocturnal 

 conditions 



Results. 



To test effects 



of green and 



red light on 



nocturnes 



To test 

 periodicity of 

 colour-change 



To test the 



periodicity of 



colour-change 



in normal and 



blinded 



specimens 



To test 

 periodicity 



To test effect 



of removal of 



the eyes, and of 



otherwise 



blinding the 



prawns, on 



periodicity of 



colour-change 



1. Effect of red and blue light on 

 " diurnal " prawns is to produce " noc- 

 turnes." Green light had no effect 

 In the control-jars a more or less green 

 colour was produced, especially in the 

 porcelain ones. 2. Nocturnes pro- 

 duced and maintained though sub- 

 jected all night to red, green, and 

 blue light derived from incandescent 

 gas flame. They persisted till next 

 morning under these conditions 

 "Light-induced nocturnes" also ob 

 tained by allowing Hippolyte to- 

 wards evening to remain exposed to 

 light in porcelain dishes. Next morn- 

 ing, however, they had recovered. 



This experiment also demonstrates 

 " periodicity," in that the habit of the 

 animal enables it to assume the noc- 

 turnal hue in spite of the continued 

 ilhimination. 



As in the previous experiment, nocturnes 

 under bright red or green light persist 

 all night and next morning iu this 

 condition, only losing somewhat of 

 their transparency the following after- 

 noon. Contrast with control speci- 

 mens which recovered next morning. 



Periodicity shown by the fact that all the 

 specimens became nocturnes the first 

 evening in spite of the constant illu 

 mination. Partial recovery ensued, 

 and this was followed by complete 

 nocturning in three cases. The same 

 occurred the following day. 



Periodicity shown. The blinded ones 

 nocturne and recover more slowly than 

 the normal. Proof lies in comparison 

 with behaviour of a specimen (C) ex- 

 posed to natural alternation of night 

 and day. 



Periodicity clearly shown, especially in 

 the small brown specimens in Flask B, 

 those in Flask Aa, and in the water- 

 circulator B. 



Experiment shows that periodicity per- 

 sists though the eyes are rendered 

 opaque or removed. The nocturnal 

 colour is assumed and the recovery to 

 the diurnal tint effected as in normal 

 specimens, but more slowly. 



