210 E. A. BAUMGARTNER 



homology of the hypophysis of the various vertebrates, based 

 on the histology alone, cannot be complete. The same is true, 

 possibly to a lesser degree, for the morphology alone. A thor- 

 ough understanding of the correlated development of both phases 

 is necessary before any homology can be satisfactory. 



The material used for this study embraces the four common 

 orders of reptiles: embryos and adults of the turtles, Chrysemys 

 marginata, embryos of Chelydra, Aromochelys odorata, Aspi- 

 donectes spinifer and Trionyx, and adults of Chrysemys picta 

 and Pseudemys elegans; embryos and adults of Alligator missis- 

 sippiensis; embryos of the lizards, Hemidactylus and Lacerta 

 agilis, viridis and muralis, and adults of Hemidactylus and 

 Sceloporus undulatus; while the snakes are represented by em- 

 bryos of Eutaenia sirtalis and Tropidonotus natrix and adults 

 of Heterodon platyrhinos and Eutaenia sirtalis. Observations 

 on the various species employed are indicated in the text and in 

 the description of the figures. 



I wish to express my best thanks to Dr. CM. Jackson of the 

 University of Minnesota for the courtesies of his laboratories 

 during the summer of 1915 and Dr. R. E. Scammon for the loan 

 of young snake embryos from the Embryological Collection of 

 the Institute of Anatomy; to Prof. H. F. Nachtrieb for per- 

 mission to study the collection of turtle embryos of the De- 

 partment of Animal Biology of the University of Minnesota; 

 to Dr. F. T. Lewis for the loan of lizard embryos from the Har- 

 vard Embryological collection; to Dr. A. G. Pohlman of St. Louis 

 University for the opportunity of studying his collection of turtle 

 embryos; to Prof. A. M. Reese of West Virginia University for 

 the loan of alligator slides; to Dr. E. S. Ruth for kindly sending 

 lizard material from the Philippine Islands; and to Prof. J. F. 

 Abbott, Dr. D. E. Jackson and Dr. Robert Gesell of Washing- 

 ton University for lizards, turtles and alligators. I have indi- 

 cated in the description of the figures the material used and the 

 laboratory from which it was obtained. 1 



1 The material used in the descriptions is designated as follows: H. E. C, 

 Harvard Embryological Collection; M. U. E. C, Minnesota University, Embryo- 

 logical Collection; R. C, Prof. A. M. Reese's Collection; W. U. C, Washing- 

 ton University Collection. 



