ENDOCRINE SYSTEM OF TYPHLOMOLGE RATHBUNI. 



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may either develop into a continuous epithelial tube or may break 

 up into a series of solid or hollow cell masses. In some animals no 

 median rudiment is found ; if this 

 condition develops i n conse- 

 quence of a complete splitting- 

 up of the median rudiment or of 

 later degeneration of the median 

 rudiment, can be decided only 

 by studying the embryology of 

 this animal. In one specimen no 

 vestiges of the thyroid are 

 present at all. If Emerson's 

 and Swingle's statements are not 

 due to an oversight, on their part, 

 of the inconspicuous epithelial 

 structures, there are now 6 speci- 

 mens of Typhlomolge known 

 which did not possess any ves- 

 tiges of the thyroid. One was 

 described by Emerson, 3 by 

 Swingle, one was found pre- 

 viously by me and the sixth 

 animal is the one described in 

 this paper. Either no thyroid 

 rudiments developed in these six 

 animals, or they were reabsorbed 

 shortly after they had developed. 

 It is certain that the thyroid 

 rudiments of Typhlomolge which 

 do persist retain permanently a 

 primitive epithelial structure and 

 fail to develop, among many 

 other structures of a normal 

 thyroid, a venous rete and the 

 colloid. 



OTHER ENDOCRINE ORGANS. 



It may be briefly mentioned that the thymus glands, the hypo- 

 physis, and the postbranchial body were found to be present in 



FIG. 8. Right thyroid rudiment of 

 Typhlomolge I. X. 340. 



