I2O 



BENNET M. ALLEN. 



tadpoles and much contracted in the operated ones. It thus 

 seems fair to conclude that in the absence of the hypophysis 

 they migrate inward from the epidermis and that they contract 

 throughout all parts of the body. In the more superficial cells 

 of the epidermis scattered pigment granules are found here and 

 there during later stages up to and beyond the 15 mm. stage. 

 These persist in both the operated and control tadpoles. These 

 observations and a careful study of the pigment cells convince 

 me that there is no disappearance and bleaching of pigment 

 granules as asserted by Smith. I differ from him further in my 

 observations of the contraction of the pigment cells in the in- 

 terior of the body in the operated tadpoles. 





FIG. 2. 



Fie. 3. 



FIG. 4. 



Figs. 2, 3, and 4 are all drawn to scale. Fig. 2 represents a 

 lateral portion of the body wall of a normal control tadpole. 

 The pigment cells can be clearly distinguished because of their 

 darker color. Fig. 3 represents a similar portion of the body wall 

 of a tadpole from which the hypophysis has been removed. This 

 shows the absence of pigment cells in the epidermis and the 

 contraction of those in the peritoneum. Fig. 4 shows a surface 

 view of a pigment cell in the peritoneum of an operated tadpole. 



