RELATION OF GLANDS TO IODINE AND METAMORPHOSIS. 407 



(Allen, '17). Swingle's experiments showed that the adminis- 

 tration of iodine alone without the mediation of the thyroid 

 gland is able to produce metamorphosis. The peculiar corre- 

 lation between the thyroid and pituitary glands made it seem 

 highly desirable to carry on experiments in feeding iodine to 

 tadpoles deprived of the pituitary gland and also to those de- 

 prived of both the thyroid and the pituitary glands. 



The results of this experiment are so definite that they seem 

 well worth recording. A large amount of caution is essential 

 in work of this kind because it has been found that the character- 

 istic color change described by Smith and Allen is not an alto- 

 gether reliable test of the successful removal of the pituitary 

 gland nor is the failure to metamorphose always to be relied 

 upon as a test of success in the removal of either the pituitary 

 or the thyroid gland. In certain cases, the color change has 

 taken place in spite of the presence of a small remnant of the 

 pituitary gland, and very greatly delayed metamorphosis has 

 been found .to take place in tadpoles in which a small fragment of 

 the thyroid gland remained after the operation for removal. 

 Notes along these lines have been published by the writer. 

 For these reasons, it seemed best to make an intensive study of a 

 limited number of specimens rather than to make a necessarily 

 cursory study of a larger number. If the thyroid gland had been 

 removed, the region where it should occur was sectioned and 

 painstakingly studied in order to determine whether the opera- 

 tion had been successful. In the majority of cases where the 

 pituitary gland had been removed, the region involved was 

 likewise sectioned and examined for vestiges 'of the gland: The 

 work was in this manner checked up to such a degree that the 

 results are offered with full confidence of their accuracy. In 

 these experiments, iodine was mixed with flour in the proportion 

 of i to 100. Water was then added to make a creamy paste. 

 This was then dried and the flakes were fed to the tadpoles. 

 In the first series of experiments, Bufo tadpoles deprived of their 

 pituitary glands were fed iodine for from ten to twenty-one days. 

 This produced most striking results as shown in Tables I. and II. 

 In this experiment, the tadpoles were kept in the same receptacle 

 and as a consequence it was not possible to follow the changes in 



