COLOR CHANGES IX SKIX OF LIZARD. 45! 



traction of the chromatophores. Firstly he points to the fact 

 that l;irva of amphibians show a different reaction to light in 

 the different stages of development. In Amblystoma Babak 

 (1910) found that the very young larvae react clearly on stimuli 

 of light, becoming dark in the light and light in the shade. The 



- then ha no influence on the color changes. After- 



wards, \\hen tin- larva- have grown older, the light has a com- 

 pleteK other effect on ilir larva?: the older larva? become li-ht 

 in tin- light and a unie a dark color in the dark. This reaction 

 take-; place under the influence of the eyes. 



According to I nli> the parietal organ, which in young larva- 

 is \\ell-de\eloped.l function to impede the contraction of 



tin- chn.matopliores. Afterwards the eyes obtain an influence 

 on the function of the pigment-cells, the illumination of the 

 then a contraction of the chromatophores. Stimu- 

 lation of the eves therefore causes in older larva? a reaction 

 opposed to ;hat caused by stimulation of the parietal eye. The 

 older the larva-, the stronger becomes the influence of the i 



ompared with that of the parietal eye. Consequently ti 

 animals become dark on a d.irk background and light on a 

 light one. 



In comparison with these different reactions towards light in 

 \oiing and older larva- of amphibians Fuchs has put forward 



li\pothc-i- that in those reptiles, which show an expansion 

 ot pi-men t in light, the impeding influence of the functioning 

 parietal organ i- present. In those reptiles which show a coii- 



1 i m of pigment in lijit according to Fuchs either the parietal 



in ha- lo-t it- function in the course of phylogeny or ontogeny, 

 or the eyes ha\e acquired, as in older larva? of amphibians, a 



ilating influence on the reactions towards light, on account 

 of \\hich the original reaction (expansion) was changed into the 

 opposite i retraction). 



In }',-,'. no parietal eye is present. The general shape 



of the organs in this region of the brain is shown in Fig. 4. The 

 epiphysis consist- ( ,f a closed pouch which by means of a -olid 

 trace of cells is connected to the roof of the diencephaloil just 

 behind the. coninii--ura habenularis superior. It is directed 



k wards and covered by a protusion of the roof of the dien- 

 , the " Xirbelpolster " of German authors. The well- 



