250 
inCHAUD ASSHETON. 
may possibly form the extreme anterior part of the heart and 
pericardium, but in any case I am inclined to think it is 
Archenteron Metenteron 
Diagrams representing sagittal sections of vertebrates at corre- 
sponding ages to show the parts of the embryo derived from the 
])rimaiy growth centre (protogenesis), and that from the secon- 
dary growth centre or blastopore lii^s (denterogenesis). The 
latter, the deuterogenetic tissues, are shaded. The dots repre- 
sent nuclei within the yolk mass and endodermal tissues of 
protogenetic origin. (From ‘ Guy's Hospital Reports,’ 1907.) 
altogether anterior to the notochord, and is connected with 
the vascular system rather than that organ. 
Text-fig. 4. 
Archenteron’ Metenteron 
