352 Agassiz on the Embryology of the Turtle. 
the same through the whole yolk mass from centre to surface, 
the greater bulk of the vitelline substance, and that the last 
cannot be homologous to the contents of the Graafian follicle, 
which bears no part whatever in the formation of the embryo, 
but is totally exterior to the Mammalian egg. Again, as will 
the amnios. At this time there are two layers all over the fey 
face of the yolk mass; the outer one, the germinal layer, he et- 
bryonic disc; the inner layer, the subsidiary layer, is quite oe 
and forms the ors 
e organs, except the cerebrospinal 
= 
