Lilian V. Sampson 497 



directed anteriorly from the body because of the large amount of yolk at 

 the sides of the embn-o; hence the dermal fold resembles an earlv stage 

 of the operculum of the tadpole in its morphological relation to the anter- 

 ior leg. 



The entire separateness of the dermal folds of the two sides recalls the 

 condition of the operculum in the two representatives of the Aglossa, 

 Dact}lethra and Pipa, where the operculum opens on both sides. In these 

 two forms, however, the anterior legs are not covered by the operculum. 



It is not evident from the points of difference and of resemblance be- 

 tween the dermal fold of Hylodes and the operculum of the tadpole 

 whether or not the two structures are homolocrotu;. 



BEAK. 



The black tip on the upper lip is seen at late stages in external views 

 (Plate II). It is triangular in sagittal sections (Fig. 0), appearing in 

 sections at about stage X. The beak does not surmount'a column of epi- 

 thelial cells like the teeth and edge of the jaw of the tadpole. It attains 

 its greatest size in the last stage within the egg, and whether by accident 

 or normally, the tip is sharp in stages XI, XII and XIII, and blunt in the 

 hatched tadpole. The facts suggest that its function is to rupture the 

 egg membrane (cf. Eana opisthodon). 



SENSE ORGANS. 



I have not attempted to make a study of the sense organs, but observe 

 that they arise in ver}' early stages as in the tadpole. 



The auditor}- vesicles are already seen in stage II. In the same stage, 

 the optic vesicles are in the condition of diverticula from the brain ; their 

 connection with the brain is reduced in the next stages, and in III the 

 lenses are being formed. Thickenings of the epidermis, the rudiments of 

 the anterior nares are present in stage III, and the hollow diverticula, 

 reaching anteriorly from the pharynx, are, to all appearances, the begin- 

 Qings of the posterior nares. 



7. COMPARISON WITH OTHER FORMS. 



In immature stages of Amphibia, there are various kinds of adaptations 

 to different surroundings. In each of the three living orders, there are 

 exceptions to the rule that the Amphibia develop from eggs laid in water 

 and jjass through a free-swimming stage. Among the Urodeles are the 

 viviparous Salamandra atra, also Saiamandra maculosa, and the* forms 

 with terrestrial eggs (some species of Amphiuma, Plethodon cenereus 

 Antodax lugubris, Desmognathus fuscaj ; among the Gymnophiona 



