REMOVAL OF THYMUS GLANDS — TADPOLES 195 



and the germ glands. The most striking facts in this connection 

 are found in the persistence of the thymus glands after castra- 

 tion. This does not show that they in their turn exert any active 

 influence upon the germ glands. In the review of literature at- 

 tention has been called to the statement of Adler that there is 

 a marked hypertrophy of the gonads in thymusless tadpoles and 

 a criticism of his claims was offered. The conclusions drawn 

 from the present work are entirely at variance with those of 

 Adler. Owing to the fact that these tadpoles were reared under 

 laboratory conditions, some of them were undersized. That is 

 true of both the operated tadpoles and the controls. In com- 

 paring the gonads of operated and control frogs of equal size, it 

 is impossible to demonstrate any consistent differences between 

 them. For instance, compare the areas — length times breadth 

 — of the male gonads of numbers 1, 12, and 15. Likewise num- 

 bers 5, 6, and 12. Also numbers 4, 6, and 20. As regards the 

 female specimens, we must first of all eliminate number 11, be- 

 cause it did not metamorphose until a year after the operation. 

 This is attributed to underfeeding under laboratory conditions, 

 a feature that is illustrated by the small size of some of the speci- 

 mens. "There appeared to be a rhythm of tendency to metamor- 

 phosis that produced transformation in the spring although the 

 tendency to metamorphosis is too weak in the fall to overcome 

 the handicap of underfeeding. During the interval, the tadpole 

 had continued to grow and the ovaries had likewise continued. 

 This resulted in their attainment of unusual size at the time of 

 metamorphosis — a fact evident not only in general dimensions, 

 but in the dimensions of the oocytes. This independence be- 

 tween the germ gland growth and the general somatic differen- 

 tiation had already been described in the case of thyroidless tad- 

 poles (Allen, '17). Taking nos. 9 and 10, we find that general 

 dimensions of ovaries and oocytes to be quite comparable to 

 those of nos. 29 and 32, although both nos. 9 and 10 have fairly 

 large ovaries. This taken in connection with the results in male 

 specimens should be convincing. Adler asserts that the removal 

 of the thymus glands causes a hypertrophy of the thyi-oid glands, 

 at the same time producing changes involving a looseness of tex- 



