304 EDUARD UHLENHUTH. 



Although I mentioned my own findings, Swingle's very definite 

 claims made the correctness of my observations doubtful, and 

 even Doctor Wilder, from whose laboratory Emerson's paper was 

 published, was ready to admit the possibility of an oversight on 

 the part of Miss Emerson. 



Immediately after my return from this meeting, I made sec- 

 tions of the 7 specimens discussed in this paper, and upon exami- 

 nation of the first one I was convinced that I was correct. In 

 response to a letter in which Swingle admitted that the organ 

 which he had claimed to be a thyroid was another vesicular 

 organ, I communicated my new observations to Mr. Swingle. 

 Neither this communication nor the incident at the Anatomists' 

 meeting has been mentioned in an account recently published by 

 Mr. Swingle in which he 1 states that 3 specimens examined by 

 him possessed no thyroid. 



The examination of the 7 specimens, together with previous 

 findings, shows that while some specimens of Typhlomolge are 

 without even vestiges of the thyroid, others possess epithelial 

 structures, evidently undifferentiated thyroid rudiments whose 

 development was inhibited by an unknown factor. 



Before describing these rudiments, the location of a normal 

 thyroid may be briefly referred to. For comparison I shall use 

 the thyroid of the Ambystomidae, which may be called representa- 

 tive of a normal Salamander thyroid. In the Ambystomida?, 

 the median thryroid rudiment splits up into two epithelial cell 

 masses, which migrate in a posterior, lateral and largely ventral 

 direction until, in Ambystoma opacum, iftiey are closely attached 

 to a large lymphatic space (Fig. i). This space is located in the 

 interstitial space formed by the muscles which surround the first 

 gill arch, ventral and median to the epibranchial of the first gill 

 arch. In other species the thyroids may be located slightly 

 further posterior, but always the lymphatic space where it is in 

 touch with the thyroid is adjacent also to the anterior cardinal 

 veins. At the site where the ventral end of the thyroid is attached 

 to the lymph space, the anterior cardinal vein comes into close 

 contact with this space, leaving there the thyroid, at its ventral 

 and posterior end, as a large vessel into which collects the blood 

 from the interfollicular rete of the thyroid. 



1 Swingle, W. W., Jour. Exp. ZooL, 1922, XXXVI., 397. 



