PHOTOPERIODISM IN REPTILES 675 



are inextricably intertwined with those of temperature; behavioral 

 thermoregulation determines the effective day length to which most 

 terrestrial reptiles are exposed and so can modify the effects of seasonal 

 changes in photoperiod. Further complications are introduced by the 

 fact that in several species of lizards the effective photoperiod is in part 

 controlled by responses of the parietal eye which is involved in the 

 regulation of the exposure to sunlight and the duration of the periods 

 spent on the surface of the ground. 



The physiological mechanisms through which the effects of day 

 length are mediated in reptiles have not been studied in detail. It is 

 possible that the pineal body is involved and possible that different 

 receptor systems cause the pituitary response in anapsid and diapsid 

 forms. 



REFERENCES 



Baker, J. R. 1947. The seasons in a tropical rain-forest. VI. Lizards (Enwia). 



J. Linnean Soc. London, ZooL, 41 , 243-47. 

 Bartholomew, G. A. 1950. The eflfects of artificially controlled temperature 



and day length on gonadal development in a lizard, Xantusia vigilis. Anat. 



Record, J 06, 49-60. 

 . 1953. The modification by temperature of the photoperiodic control 



of gonadal development in the lizard Xantusia vigilis. Copeia, 1953, 45-50. 

 Bogert, C. M. 1949. Thermoregulation in reptiles, a factor in evolution. 



Evolution, 3, 195-211. 

 Bullock, T. H. 1955. Compensation for temperature in the metabolism and 



activity of poikilotherms. Biol. Revs., 30, 311-42. 

 Burger, J. W. 1937. Experimental sexual photoperiodicity in the male turtle, 



Pseudemys elegans (Wied.). Am. Naturalist, 71, 481-87. 

 Cieslak, E. S. 1945. Relations between the reproductive cycle and the pituitary 



gland in the snake Thamnophis radix. Physiol. ZooL, 18, 299-329. 

 Clausen, H. J., and E. G. Poris. 1937. The effect of light upon sexual activity 



in the lizard, Anolis carolinensis, with especial reference to the pineal body. 



Anat. Record, 69, 39-53. 

 Cole, L. C. 1943. Experiments on toleration of high temperature in lizards 



with reference to adaptive coloration. Ecology, 24, 94-108. 

 Cowles, R. B., and C. M. Bogert. 1944. A preliminary study of the thermal 



requirements of desert reptiles. Bull. Am. Mus. Nat. Hist., 83, 261-96. 

 Dawson, W. R., and G. A. Bartholomew. 1956. Relation of oxygen consump- 

 tion to body weight, temperature, and temperature acclimation in lizards 



Uta stanshuriana and Sceloporus occidentalis. Physiol. ZooL, 29, 40-51. 

 Dessauer, H. C. 1955a. Effect of season on appetite and food consumption of 



the lizard, Anolis carolinensis. Proc. Soc. Exptl. Biol. Med., 90, 524-26. 



