Lilian Y. Sampson 501 



embryos, and numerous folds on the sides of the embryo probably func- 

 tion as respiratory organs." 



In other forms besides Hylodes, the tail differs from the swimming- 

 tail of the tadpole. In Nototrema marsupiatum it is said to be vascular ; 

 in the tadpoles of Hyla abbreviatus, Avhich slip about (even before their 

 legs appear) on moist perpendicular rocks, the ventral fin is flattened, 

 and seems to serve as a sucker ; in Ehinoderma darwinii the tail is small 

 and weak. In Hypogeophis and in Autodax, the fin is wanting. 



Lastly, in Hy lodes and in Eana opisthodon the little median horny tip 

 in the upper lip is found in a late embryonic stage, and is used in the 

 latter, at least to rupture the membranes in which the embryo is so long 

 encased. 



In conclusion, we find that the Amphibia are a plastic group, and 

 among Anura especially there are patent examples of the adaptation of 

 the larval stages to new external conditions, while the original plan of 

 structure of the adults has remained unchanged. There are also other 

 forms known in which, although the adults are very similar, the embryos 

 have different modes of development. In such cases we must suppose 

 that the embryos have diverged in their development while the end-result 

 of their development, namely, the adult form, has remained virtually 

 unchanged. For example, there are two species of Peripatus very simi- 

 lar in adult stages, but which arrive at the adult form through dissimilar 

 embryonic stages. There are also various species of Alpheus and of 

 Palaemonetes that have very similar adults, but whose embryonic meta- 

 morphosis differs according to the degree of abbreviation of the develop- 

 ment of the different species. 



Furthermore as Wilson has pointed out in this connection, it has been 

 shown in the Ascidians that the same adult form may be produced by 

 methods as different as budding and development from the egg. Finally, 

 it is well established that in certain animals mutilation, or even removal 

 of parts of the egg, does not prevent the development of a normal embryo. 



SUMMARY. 



Comparing the development of Hylodes with the development of frogs 

 having a tadpole stage, the following points of resemblance and of differ- 

 ence are apparent: 



" We find not only in embryos but also in adult amphibia, great diversity 

 in breathing; respiration may be carried on by the mouth, the skin and 

 even, according to Ritter and Miller, by vascular toes in Antodax, Plethodon 

 and Brachoceps. 



