130 BENNET M. ALLEN. 



SUMMARY. 



1 . The removal of the anlage of the anterior lobe of the hy- 

 pophysis early causes the pigment cells to contract, and those of the 

 epidermis to withdraw from it into the interior. This takes place 

 while the gland shows little or no apparent histologicaf differ- 

 entiation. 



2. Evidence has been given to show that the absence of the 

 hypophysis in tadpoles makes them highly susceptible to un- 

 favorable chemical conditions of the water. This will be tested 

 out specifically in later experiments. 



3. The absence of the hypophysis causes either directly or 

 indirectly a failure to undergo metamorphosis especially evident 

 in the absence of limb growth beyond a very rudimentary con- 

 dition. 



4. The absence of the hypophysis causes a marked diminution 

 of colloid formation in the thyroid gland and in the stage of 24 

 mm. involves a retardation in its growth. 



5. During the stages studied the absence of the hypophysis 

 produced no noticeable effects upon the thymus gland nor upon 

 the gonads. 



LITERATURE. 

 Adler, L. 



'14 Metamorphosestudien an Batrachierlarven. I. Extirpation endocriner 

 Driisen. II. Extirpation der Hypophyse. Arch. f. Entw. mech. d. Or- 

 ganis., Bd. 39. 

 Allen, B. M. 



'16 Extirpation Experiments in Rana pipiens Larvae. Science, November 24, 



1916. 

 Smith, P. E. 



'16 Experimental Ablation of the Hypophysis in the Frog Embryo. Science, 



August 25, 1916. 

 Smith, P. E. 



'16 The Effect of Hypophysectomy in the Early Embryo upon the Growth and 

 Development of the Frog. Anatomical Record, October, 1916. 



