SOME PHASES IN THE DEVELOPMENT OF CHRYSEMYS 



CINEREA* 



By Bert Cunningham 

 Plates 2-4 



Introduction 



The esrg production, egg-laying habits, nest building, and the de- 

 velopment of the embryo through the gastrulation stage in Chrysemys 

 cinerea are dealt with in this paper. A satisfactory method of arti- 

 ficially incubating the eggs has made it possible to secure consecutive 

 stages of development in such numbers that careful study could be 

 made of many points which have caused dispute. 



Many details of turtle embryology have been worked out, but there 

 has been little collection or unification of these data. Since several 

 forms of turtles were used by the various writers, it will be impos- 

 sible to limit the discussion of the literature to even a single genus, 

 and the contradictory opinions of these writers as to developmental 

 history probably resulted from the uses of a variety of forms. 



As early as 1828 Tiedmann published a report upon two eggs of 

 Emys amazoni. This was followed by the description (exact title 

 unknown) of a turtle egg seven days old by Cams in Februarj^, 1829. 

 In the same year Berthold discussed the absence of the chalaza in the 

 egg of Emys. An account of a young egg of Emys europaea was pub- 

 lished by Von Baer in 1834. Three years later he published ''Ueber 

 Entwicklungsgeschichte der Thiere, " Teil II, in which he points out 

 the similarity of structure of the eggs of the chick and the turtle, 

 and the greater time required for the development of the latter. His 

 conclusions were based upon the observations of Carus and Tied- 

 mann. He noted also that while the ovary and oviduct of the chick 

 is single, that of the turtle is paired. Peters (1838) published an 

 article upon a young " Schildkroete. " Rathke, who is often credited 

 with the first embryological work on Chelonians, began his contri- 

 butions to embryology in 1832 with an account of the " Wolff scher" 



* Tbp writer wisVies to express his appreciation to the Zoological Staff of the Univer- 

 sity of Wisconsin, esijprially tn Dr. E. A. Smith, Dr. M. F. Guyer, and Dr. A. S. Pearse 

 for helpful suggestions and criticisms. 



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