238 RITTER. 
EXPLANATION OF PLATE XVII. 
Fic. 72. An early stage in the formation of the ganglio-hypophyseal Ax/age 
before its separation from the endoderm. Camera drawing as far as possible with 
Leitz. oc. 5, obj. 7. 
Fic. 73. Shows a stage in the formation of the ganglion somewhat more 
advanced than the preceding, the whole section drawn in order to show the distri- 
bution of the blood or mesenchyme cells in the body space. X 210. 
Fic. 74. From the same series as Fig. 73, more highly magnified, showing the 
supposed evagination to form the ganglio-hypophyseal Az/age. X 508. 
Fic. 75. Longitudinal section of the ganglion and duct, the former almost 
separated from the latter. X 250. 
Fic. 76. Transverse section of the duct, with its dorsal wall considerably 
thickened for the formation of the ganglion. X 508. 
Fics. 77 and 78. Two sections in which cells appear to be breaking away from 
the endoderm, and passing into the body space to become mesenchyme cells. 
Both of these cases are far from the position where either heart or ganglion will 
form. X 720. 
