3IO EDUARD UHLENHUTH. 



accomplished, and thus was dislocated from its primary median 

 position to wards the left side. 



The 6 specimens described so far died on the way from Texas 

 to New York, shortly after they had been removed from the caves. 

 The seventh animal, Typhlomolge I, a specimen of 97.5 mm., 

 died after it had been kept alive in the laboratory for 14 months. 

 The largest part of this time (12 months) it lived at a tempera- 

 ture of 15 C. and in darkness; for the last two months it was 

 kept in an aquarium stocked with plants, small crustaceans and 

 young tadpoles, in daylight and at a temperature of approxi- 

 mately 22 to 25 C. The sections of this specimen are greatly 

 torn and I am not sure that our inability to find a median and 

 left lateral rudiment is due to the absence of these organs and not 

 to the poor condition of the sections. On the right side, how- 

 ever, a lateral rudiment is present. It is located near the lymph 

 space, anterior and dorsal to the location of the main portion of 

 the thyroid of Ambystoma opacum and resembles more closely a 

 thyroid structure than the rudiments of the specimens described 

 previously. It consists of a small number of hollow vesicles 

 which compose an elongate, egg-shaped organ possessing a 

 connective tissue capsule and hence impressing one as a distinct 

 and individual organ. The walls of the vesicles are of epithelial 

 character; but no colloid is contained in the lumen of the vesicles 

 (Fig. 8). 



Summary: Although Typhlomolge, in its advanced stages, does 

 not possess an organ resembling the normal thyroid of a sala- 

 mander, epithelial structures are found which indicate that in 

 the young embryo of this animal the thyroid rudiment forms in a 

 similar manner as in other amphibians. This rudiment, however, 

 for some reason, fails to develop into a thyroid. In some animals, 

 development ceases after the median epithelial outgrowth has 

 separated from the pharyngeal epithelium and the rudiment 

 remains a single vesicle. In other cases it may partly split up 

 into lateral portions which, as in other salamanders, move in a 

 posterior direction and, in some instances, may approach closely 

 the lymph space; but they never reach the anterior cardinal vein. 

 The unsplit part of the median rudiment may retain its median 

 position and primitive vesicular structure; the lateral portions 



