Castle. — Uiona iutestinalis. 



PLATE XI. 



Magnification of all Figures, 560 diameters. 



Fig. 71. 11 2- cell stage, dorsal view. 

 Fig. 72. Early gastrula, dorsal view. 



Figs. 73-77. Five cross sections through an early gastrula (128-cell stage). For 

 position of sections in embryo, see horizontal lines 73-77 in Fig. 72. 

 Note. — Consult general statement regarding lettering under Explanation of Plates. 

 Fig. 78. Sagittal section through au early gastrula (older than that shown in 



Fig. 72). 

 Fig. 70. Similar section through a slightly older stage. 

 Fig. 80. Surface (dorsal) view of late gastrula. 

 Figs. 81-83. Three horizontal sections from a series through a late gastrula. 



