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SCIENCE 



[N. S. Vol. XLIV. No. 1143 



pophysis ingrowth. When this is performed at 

 the stage of from 3.5-4 mm. total body length 

 the hypophysis anlage can be readily seen and 

 removed. The wound heals in from 20 to 30 

 minutes and the tadpoles quickly recover. . In 

 the course of these experiments the anlage was 

 successfully removed from 430 tadpoles. 



This phase of my work was duplicated by 

 Dr. P. E. Smith, 2 who published a preliminary 

 account of his work in the August 25, 1916, 

 number of Science. During the month of 

 July prior to this time I had the pleasure of 

 discussing my work with Dr. Smith at Berke- 

 ley. Previous to this time I had no knowledge 

 of his work nor of his plans and he assures 

 me that he was equally ignorant of my work. 

 We both presented papers upon our experi- 

 ments at the meeting of the Western Society 

 of Naturalists at San Diego, August 9 to 12. 

 On the 7th of June, before starting west, I 

 demonstrated specimens and explained my re- 

 sults to a number of scientists, including Pro- 

 fessor Frank B. Lillie, Dr. Emil Goetseh, Dr. 

 Chas. H. Swift and a number of others whom 

 I met in Chicago at that time. It is thus clear 

 that these experiments were independently con- 

 ceived by Dr. Smith and myself and that we 

 worked contemporaneously upon them each 

 without knowledge of the other's work until 

 July, 1916, two months after the experiments 

 had been performed. It was impossible to give 

 an earlier report upon this work because the 

 experiments upon thyroid removal required a 

 long period of time to establish definite re- 

 sults. 



Our results are in accord in showing that 

 the removal of this gland has an early effect 

 in producing a great contraction of the super- 

 ficial pigment cells. The results in my speci- 

 mens were very striking. I found that my tad- 

 poles assumed a uniform creamy silver color. 

 This change was evident on the seventh to 

 eighth day after the operation. Our work is 

 further in accord in that we both observed a 

 retardation in growth very marked in my ma- 

 terial and a striking retardation in the de- 

 velopment of limbs. The buds appeared but 



- Smith, P. E., ' ' Experimental Ablation of the 

 Hypophysis in the Erog Embryo," Science, Au- 

 gust 25, 1916, p. 280. 



remained very small. One specimen kept alive 

 until August 30 had only reached a length of 

 30 mm. and the limb buds were still extremely 

 small after the controls had all fully meta- 

 morphosed into frogs. Through all this time 

 it maintained its silvery color. 



Dr. Smith found that there was no more 

 mortality among his operated tadpoles than 

 among the controls. This is quite contrary to 

 my experience; but is no doubt explainable 

 upon the grounds that he had a more favorable 

 water supply than ours. In my experiments 

 upon removal of the hypophysis there was a 

 very heavy mortality. I am convinced that 

 this must be explained upon the ground that 

 the presence of the hypophysis anlage is neces- 

 sary for the proper adjustment of the tad- 

 poles to these injurious influences. It might 

 be mentioned at the outset that in roughly 

 one third of the operated tadpoles the upper 

 part of the mouth was defective. This was 

 due to the removal or disturbance of its anlage 

 in the operation. These tadpoles were of 

 course doomed to die, but this can not account 

 for the fact that in one experiment in which 

 30 were operated only 4 remained alive at the 

 end of 33 days. 



In another experiment the case was made 

 still more clear. Of 100 operated tadpoles only 

 7 remained alive at the end of 32 days — of 

 these there had been failure to remove the 

 hypophysis in one case and in another there 

 had probably been partial failure. A control 

 set was reared in which the cut was made as 

 though for removal of the hypophysis, but the 

 gland was left intact. Of the 28 thus treated 

 14 were alive at the end of 42 days. At this 

 time they were in a very flourishing condition, 

 although the operation caused a temporary 

 retardation of growth. 



In other sets of experiments there were usu- 

 ally one or two tadpoles that failed to show the 

 characteristic color change. These were in- 

 variably hardy. Upon sectioning them the 

 hypophysis was found intact. 



Operated tadpoles and control lots were kept 

 side by side in the same or neighboring aquaria 

 and the operated ones invariably showed heavy 

 mortality while the control tadpoles were 

 healthy. This mortality did not appear until 



