252 HENRY LAURENS 



removed, the reactions of the melanophores would cease to 

 take place. 



As an interesting fact von Frisch found this region of the roof 

 of the diencephalon to be also particularly easily stimulated 

 by other means than light, e.g., electric currents (pp. 335, 336, 

 and 376) in this particular fish Phoxinus. 



Von Frisch (p. 377) is led to make the suggestion, later taken 

 up by Fuchs, that perhaps in other animals the parietal organ 

 may be found to have an influence on the pigment cells and that 

 thereby an explanation may be found for some of the perplexing 

 diverse results, e.g., in tadpoles, where darkness causes the 

 melanophores to contract and light causes them to expand, 

 while the opposite reactions take place in the adult frog, and 

 in Axolotl larvae, citing Babak's results on normal and blinded 

 individuals. Also for the reactions of the melanophores of 

 Salamandra maculosa larvae and of Triton cristatus adults which, 

 however, show an expanded condition of the melanophores in light 

 and in both normal and blinded individuals. 



However, he has himself (p. 378) carried out experiments with 

 Salamandra larvae and adult Tritons with different results than 

 he hoped for. For in these animals illumination of the head 

 region did not give as clear results as in Phoxinus. Further- 

 more he received the impression that local illumination of any 

 portion of the body results in an expansion of the melanophores 

 of the whole body. In other words the illumination of the 

 portion of the body under which the epiphysis is has no different 

 effect from illumination of any portion of the body. 



Experiments such as von Frisch suggests should be carried 

 out on tadpoles and frogs, in some of which the parietal or- 

 gan has been destroyed, in others of which the influence of the 

 eyes has been removed, etc. In these animals the pineal organ 

 attains a comparatively high degree of development (Studnicka, 

 p. 110 IT.) Furthermore these results should be compared with 

 those obtained with such an animal as Diemyctylus, where the 

 reactions of the larval melanophores are also opposite to those 

 of the adult, but where there is no pineal organ and where the 

 epiphysis is not highly developed. The results of such experi- 



