THU 
78. 
MUSEUM OF COMPARATIVE ZOOLOGY. 103 
PLATE XII. 
Sagittal section (left-hand surface) from an embryo somewhat older than 
the preceding. 
Sagittal section of the lungs at about the time of hatching. 
Sagittal section of the lungs five or six days after hatching; the upper 
and lower walls of each lamella are connected by the union of the 
nuclei (z/.). 
Sagittal section showing the nervous system at the beginning of reversion. 
Sagittal section of the cephalothorax at the time of hatching, to show the 
post-stomodeal portion of the alimentary canal, and also the concen- 
trated condition of the ventral ganglionic mass. 
