546 William A, Hilton. 



limb buds may be readily recognized from surface views. Soon 

 after this, pigment develops and the embryo begins to make marked 

 movements within the egg membranes. A section of this stage, Fig. 

 64, shows the solid mass of yolk cells much as they were seen in 

 earlier stages, but the cell walls begin to be lost. About the whole 

 yolk mass, a thin dark line of ectodermal tissue may be seen and 

 under it and next to the yolk many loose mesenchymal cells. 



Several interesting things are illustrated in the development of 

 Desmognathus : 



1. The segmentation is at first partial and then total. 



2. The blastopore formation is much like other Amphibia from the 

 surface, but seems to be entirely different from other forms described 

 in the way the cells go to form the archenteron by growing down into 

 a nearly solid mass of yolk. 



3. The early separation of the embryo from the yolk mass, resem- 

 bles to a marked degree the position of the embryo in certain mero- 

 blastic eggs. 



I wish to thank Prof. B. F. Kingsbury and Prof, and Mrs. S. H. 

 Gage for aid and encouragement in the preparation of this paper. 



SOME IMPORTANT REFERENCES. 



Eycleshymer, a. C, '95. The Development of Amblystoma punctatum. Jour. 

 Morph., Vol. X. 



, '04. Bilateral Symmetry in the Egg of Necturus. Anat. Anz., Bd. 



XXV, Nos. 9 and 10, p. 230. 



IIay, O. p., '88. Observations on Amphiuma and its Young. American Nat- 

 uralist, Vol. XXII, No. 257. 



Hilton, W. A., '04. Segmentation of the Ovum of Desmognathus fusca. 

 American Naturalist, Vol. XXXVIII, p. 498. 



Jordan, Edwin O., '93. The Habits and Development of the Newt Diemyc- 

 tylus viridescens. Journal of Morphology, Vol. VIII, No. 2, p. 269. 



McGregor, J. Howard, '96. An Embryo of Cryptobranchus. Proc. N. Y. Acad. 

 Sc, Dec. 14. Abstract in Zool. Anz., Bd. 20, p. 29. 



Montgomery, Th. H., '01. Plethodon embryo. Proc. Phila. Acad of Sc. 



RiTTER, W. E., AND MiixER, LoYE, '99. A Contribution to the Life History of 



Autodax lugubris, a California Salamander. American Naturalist, Vol. 



XXXni, No. 393, p. 091. 



