80 University of California Publications in Zoology [Vol. 11 



Mar. 25. All tadpoles the same color. 

 Apr. 1. All tadpoles the same color. 

 Apr. 11. Of the four remaining tadpoles on liver plus phloroglucin, two 



are as dark as the six tadpoles fed on liver alone, and two are 



slightly lighter. 



The same experiment witli albumen as food gives the follow- 

 ing results (table 15) : 



Table 15 

 Length measurements of tadpoles fed on albumen, albumen + reaorein, 



and albumen + phloroglucin. Measurements represent the average 



length of all the tadpoles in the dish. 



Hyla. Experiment started Mar. 18, 1912 



Length in mm. 



Pood Mar. 25 



Albumen 13.6 



Albumen + resorcin 13.1 



Albumen 4- phloroglucin 12.8 



Mar. 25. Tadpoles fed on albumen plus phloroglucin are very slightly 

 lighter than the other two sets, which are both the same color. 



Apr. 11. Tadpoles fed on albumen plus phloroglucin are very slightly 

 lighter than those on albumen, but the difference is scarcely 

 noticeable. 



This group of experiments, as will be noted, was tried but 

 once and with a small number of tadpoles, so they can be regarded 

 only as a beginning in this direction. The results indicate that 

 the various substances may affect the color of the tadpoles to 

 some extent. 



H. HIST0L0C41CAL DIFFERENCES BETWEEN CHEOMATOPHORES 

 OF LARVAE FED UPON DIFFERENT FOODS 



The statements as to the color differences in the tadpol&s have 

 been made thus far on the basis of their appearance to the 

 unaided eye. The differences as shown by the microscope are no 

 less marked and show plainly that there is actually less pigment 

 in the egg-fed tadpoles (plate 1). 



With the low powers of the microscope the black epidermal 

 chromatophores of the dark liana tadpoles appear to be greatly 

 branched, and so filled with pigment that they come very close 



