PART I, PLATES 



FIGURES 1 TO 28 



The series here figured and de.scribed are in the embryological collection of 

 Columbia University, with the exception of series Si, which belongs to the em- 

 bryological collection of Princeton University. I am greatlj' indebted to Prof. 

 C. F. W. McClure for the oi)portunity of studying this series and publishing the 

 eight sections shown in figs. 245 to 251. 



