ON THE COLOR CHANGES IN THE SKIN OF THE 

 LIZARD PTYCHOZOON HOMALOCEPHALUM. 



DR. H. BOSCHMA, 

 ZOOLOGICAL LABORATORY OF THE UNIVERSITY OF LEYDEN. 



The Javanese lizard Ptychozoon homalocephalnm Crvdt. can 

 change its color in some degree in connection with the difference 

 in the color of its surroundings. In bright sunlight the dorsal 

 surface of the animal is light gray with the exception of a number 

 of pronounced blackish brown stripes which have a zigzag course 

 in transversal direction and some spots of the same color at the 

 lateral parts of its head and neck. In strongly shady surround- 

 ings the color of the skin between the transversal stripes darkens 

 and assumes almost the same dark color as the stripes, which 

 thereby become almost invisible. With these animals, which 

 very commonly occur in 's Lands Plantentuin at Buitenzorg I 

 have made some experiments to make out whether the change 

 of color is controlled by the vision of the animals or if it is only 

 due to the influence of light acting on the skin directly. 



The experiments were made in August 1921 in the Treub- 

 laboratorium at Buitenzorg with animals captured in the Plan- 

 tentuin, in most cases by natives. I kept the animals in glass 

 vessels with a diameter of about 20 cm., the bottom and sides 

 of which were covered by white paper or black velvet. In 

 these vessels they behaved quite calmly. The experiments con- 

 sisted in the comparison of the color of the skin of the same 

 animal (i) in a white-covered vessel, (2) in a black-covered 

 vessel, and (3) in a white-covered vessel whilst its eyes were 

 covered with a not transparent cap. The latter consisted of 

 the cut-off digit of a rubber glove, in the top of which a small 

 hole was cut. This cap was pushed over the head of the animal. 

 It covered its eyes and the greater part of its head and neck, 

 whilst the end of the snout was free and the respiration was not 

 hindered. When the animal had Uvn in the same conditions 

 for some time (at least a quarter of an hour) I noted the color 



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