646 F. W. GAMBLE AXD F. \V. KEEBLE. 



control (I), become greenish or greenish blue at 7.10; but 

 when again examined at 9.5 p.m. the normal specimen was 

 (as is usual with uninjured Hip poly te) a full nocturne. (C) 

 was partially nocturnal, but recovered to brown after five 

 minutes' exposure to white light. 



Both these experiments show that the difference in beha- 

 viour between amputated and normal specimens is due in part 

 to the effect of shock, in part to the loss of sight, and hence 

 that the direct action of these changed light conditions on 

 the chromatophores themselves is negligible. A series of 

 camei'a drawings of amputated nocturnes exposed to light, 

 PI. 35, figs. 29—32, exhibits the flow of red and yellow pig- 

 ments from the centre to the branches of the chromatophores. 



So far we have dealt with the results of the elimination of 

 the eye's action during the diurnal phase. Amputation of the 

 eyes of a full nocturne at 9.15 p.m., August 5th, caused no 

 immediate colour-change, nor had any change occurred at 

 9.40 nor at 10.25 p.m. 



Stimulation by Section of the Ventral Cord, by 

 Ether, Electricity, and Change of Temperature. The 

 nocturning and recovery of amputated specimens indicates 

 that the periodicity does not reside in the eye and optic 

 ganglia, but is a function of the rest of the nervous system. 

 The colour-effects produced by the response of this system to 

 various forms of stimulation have now to be considered. 



A verv curious result is obtained by section of the nerve- 

 cord in the middle region of the abdomen just below the 

 " hump " or line of flexure of the tail. The behaviour of 

 nocturnes may first be mentioned. 



The cord of a large full nocturne was cut just below the 

 " hump,^' and the prawn was then exposed to light in a white 

 porcelain dish. The tail region recovered first and almost 

 immediately after the operation. The head recovered some- 

 what later, while the middle part of the body retained its 

 nocturnal colour after half an hour's exposure to light. The 

 sudden shock may be pictured as setting up impulses 

 which, besides effecting violent contraction of the swimmerets, 



