WEYSSE. — BLASTODERMIC VESICLE OF BUS SCROFA. 321 



EXPLANATION OF PLATES. 



All the drawings were made with the camera lucida directly from the object 

 itself, with the exception of Fig. 2, Plate I., which is a graphic reconstruction 

 made from sections drawn with the camera. In the case of all transverse sec- 

 tions it is the posterior face of the section that is shown, so that right on the 

 figure corresponds to the right side of the disk. The embryos came from four 

 uteri, and may accordingly be grouped as follows : A, Figs. I, 3, 4, 10, 27 ; 

 B, Figs. 2, 21, 22, 23, 26 ; C, Figs. 5, 6, 14-20, 24, 25 ; D, Figs. 7, 8, 9, 11, 12, 13. 



VOL XXX. (n. S. XXII.) 21 



