HIPFOLYTK VARIANS. 647 



inhibit the normal tonic impulses which hold the red and 

 yellow pigments retracted. The tardiness of the middle 

 region of the body to recover is perhaps due to the structural 

 peculiarity of the nervous connections with the chromatophores 

 of that region, since, in the course of recovery of intact 

 animals from the nocturnal condition, the middle i-egion is 

 frequently bluish green when the head and tail are brown. 



Eeturning to the effect of section of the cord in intact 

 Hippolyte, we record the result in a brown specimen which 

 was put in the dark after the operation. At 7 p.m. it was 

 examined and was found to exhibit a full nocturnal tint 

 behind the eyes, while the region of the tail, just in front of 

 and behind the line of section, had remained brown. 



In this connection experiments made by immersing Hippo- 

 lyte in a mixture of ether and sea water, may be mentioned. 

 Intact and eye-amputated (brown) specimens react to this 

 mixture in a similar way. They exhibit no immediate colour- 

 change, but when taken out and placed in a current of sea 

 water a green effect frequently appears just behind the eyes 

 and extends back to the hinder end of the carapace, the 

 remainder of the body resting unchanged or becoming lighter 

 and more transparent. Intact specimens, in twenty minutes 

 or so, revert to their original colouring or remain somewhat 

 lighter. Amputated specimens exhibit the green effect more 

 conspicuously as a rule, but also recover in a short space of 

 time. 



An even more mai'ked change of the same kind is obtained 

 by painting the eyes with collodion. Here the operation is 

 complicated, involving blindness and ether-poisoning. The 

 green effect took place all over the body (on brown speci- 

 mens), but subsequently passed away. A second coat re- 

 induced the change, from which, as well as from the ether- 

 experiments, it seems clear that tlie green effect is due to the 

 action of the ether on the central nervous system — possibly 

 (in the case of painting the eyes) on the optic ganglia. 



The action of the interrupted electric current is somewhat 

 similar. Thus if a "light-induced nocturne" is exposed to 



