633 
of SELENKA. In Pteropus edulis the vesicle is also formed as in the 
human but it fills the cavity of the chorion completely. Then there is 
a sort of invagination (SELENKA, Studien, Fig. 6, Taf. 41) which is 
the beginning of the amnion. Beginning therefore in Pteropus and 
passing through the stage of our embryo to Graf SPEE’s we have new 
and quite definite data regarding the formation of the blostodermic 
membranes and amnion of the human embryo. These are represented 
in the following diagrams. 
Fig. 2. Diagrammatic representation of the formation of the membranes in the 
human embryo. 1, Solid embryonie dise 2 first formation of a vesicle; 3, the human 
embryo of this paper; 4 and 5, hypothetical stages to show the closures of the invagi- 
nation and the formation of the umbilical vesicle; 6, diagrammatic section of Graf SPpEE’s 
embryo; ch, chorion; a, invagination and amnionie cavity; al, allantois; wu, umbilical 
vesicle. 
A more detailed description of this embryo is reserved for a 
future publication. 
4 
