Frank A. Rtromsten 455 



the embryology of turtles the fact that " In the Old World, no turtles 

 are found in the immediate vicinity of the great centers of study.'" 



Eathke. 48, in his monograph. "Ueher die- EniwicMnng der ScJiild- 

 kroeten," merely mentions the presence of some of the larger veins in a 

 few of the earlier stages. - His older embryos were so poorly fixed that 

 it was not possible for him to trace the advanced stages of venous devel- 

 opment. Agassiz's remark that, " It is felt, on almost every page of 

 his work, that he labored under a scarcity of materials which con- 

 stantly impeded his progress/' is particularly true in respect to his treat- 

 ment of the venous system. 



About ten years later, Agassiz,. 57, undertook to " write anew the em- 

 bryology of this order of reptiles," that he might continue the work 

 which Eathke was unable to complete. His investigations, which are 

 published in a large volume of nearly two hundred quarto pages, together 

 with thirty-two plates, are concerned chiefly with the study of the emliryo 

 as a whole without the aid of serial sections. Hence, almost no atten- 

 tion is paid to the development of the intra-embryonie veins, although 

 cousideraI)le space is devoted to the consideration of the vitelline circula- 

 tion. 



It is thus seen that no serious attempt has hitherto been made to give 

 a complete history of the development of the veins of turtles. On the 

 other hand, very careful and accurate observations have been made bv a 

 number of investigators on the embryology of the veins of snakes and 

 lizards. Eathke, 39, Hoffmann, 90, Hochstetter, 93, Grosser and Bre- 

 zina. 95, and Choronshitzky, 99, have investigated in whole or in part 

 the development of the venous system in these reptiles so that our knowl- 

 edge here is quite complete. 



The purpose of the present paper is: (1) to confirm the work already 

 done on reptiles by other writers, and to furnish another link in the 

 comparative embryology of the venous system of amniota ; (2) to inves- 

 tigate somewhat more in detail than has hitherto been done the changes 

 which the uml)ilical veins undergo, and their ultimate relations to the 

 abdominal veins. . As a basis, therefore, for comparing the various stages 

 of venous development in Chelonia with those of other reptiles, a brief 

 resume of tlie chief results of Hochstetter's (93 and 03) papers is given 

 below. 



DEVELOPMENT OF THE VEINS OF LACERTA AND TROPIDONOTUS. 



According to Hochstetter, the first veins to appear in reptiles are the 

 omphalo-mesenterics. These are shortly followed by the precardinals, 

 the postcardinals, and tlit^ uml)ilicals. 

 35 



