634 William A. Hilton. 



The eggs of Spelerpes resemble those of frogs and toads in many 

 ways, while the eggs of Desmognathus, Plethodon; Autodax lugubris. 

 Necturus maculatus and a few more Urodela resemble each other in 

 a number of features and seem to be more fish-like in their devel- 

 opment. 



The first description of any of the stages of development of Des- 

 mognathus fusca was made by Prof. H. H. Wilder, March, 1899. 

 A few rather advanced embryos were described and figured. The 

 embryos were found to be strikingly like those of fish, with a large 

 yolk-sac well separated from the body of the animal. Judging from 

 these stages there seemed to be good reason for supposing the segmen- 

 tation to be like that of fish or meroblastic. In September of the 

 same year, Ritter and Miller described the eggs and some of the stages 

 of later development of Autodax lugubris. In this form they found 

 the eggs to be very large, as much as 5 mm. in diameter, and the 

 position of the embryo on the yolk-sac was strikingly like that de- 

 scribed by Wilder for Desmognathus. ]^o evidence was brought for- 

 ward to show that the eggs were meroblastic, although such a type 

 of segmentation was suspected. Montgomery described some rather 

 late stages of Plethodon development and from his study it was 

 learned that the so-called yolk-sac remained divided into distinct 

 cells or blastomeres until a rather late stage when all the cell out- 

 lines became lost and the blastomeres were fused together. 



In 1904 H. H. Wilder and the author both published short articles 

 on the early development of Desmognathus fusca and both papers 

 showed without a doubt that the segmentation Avas holoblastic and 

 not meroblastic. Dr. Wilder's evidence was from surface views, 

 the other was from sections as well, and in the latter it was found 

 that although after a time the segmentation became total, at first it 

 was not so. 



The present paper is a continuation of the study of early develop- 

 ment. Only an outline of the early stages up to embryo formation 

 will be given. At another time I hope to be able to consider some 

 phases of blastopore formation and later embryonic development more 

 in detail. 



The following observations on the eggs of Desmognathus fusca 



