CHAPTER 21 



THIRD PART OF flBER ENTWI CKLUNGSGESCH I CHTE Continued] 

 DEVELOPMENT OF REPTILES, MAMMALS, AND ANIMALS DEPRIVED OF 



AMNION AND YOLK SAC 



Baer based his presentation of reptile development on data 

 concerning turtles, monotremes, and viviparous snakes and 

 lizards C§ 8). The aim of his detailed study, according to 

 Baer, was comparison of the peculiarities of development 

 characteristic of the separate classes with features character- 

 istic of all vertebrates. 



Baer's information about turtle development was limited. 

 His attempts to receive more or less late stages of development 

 were unsuccessful, as described in detail in his specialized 

 study. 1 (1°3) The peculiarities of early turtle development, 

 which Baer observed up to the tenth day of development, showed 

 that interpretation of the embryo was an error of observation 

 CFigure 30). In UBER ENTWICKLUNGSGESCHICHTE, Baer 

 referred to the observations of Tiedemann,2 who saw a turtle 

 embryo surrounded by amnion. The urinary sac is connected with 

 the urinary bladder and by the right side rather than in the 

 body of the embryo. The yolk sac, by the help of the yolk duct, 

 is united with the intestine. As in birds, towards the end of 

 embryonic life, the yolk sac passes through the umbilicus to the 

 abdominal cavity. Bending of the embryo and its internal 

 organization is the same as that of birds. 



Concerning the monotremes, snakes and lizards, Baer 

 enumerated in detail the similarities of their embryonic 



1. K. E. v. Baer. "Beitrag zur Entwickelungsgeschichte der 

 Schildkroten." ARCH. ANAT . PHYSIOL. U. WISS. MED. 

 C1834) , pp. 544-550 (104). 



2. (Ed.: Friedrich Tiedemann, ZU SAMUEL V. SOMMERINGS 

 JUBELFEIER. Heidelberg, 1828, pp. 23 ff.) 



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