No details are given as to the structure of the chorion or the presence of villi upon it.
In the Cheiroptera (Vespertilio and Pteropus), the yolk-sack is large, and coalesces with part of the chorion.
This form of placenta occupies a broad zone of the chorion, leaving the two poles free.
From the whole surface of the chorion there project branched vascular processes, covered by an epithelium.
In the lower part of the egg-tube the epithelium gives rise to a chorion.
The chorion with its vascular processes surrounds the whole embryo.
The first thing that is formed is the amnios; the next the chorion; and they enwrap the seed round like a curtain.
The decidua reflexa and serotina together envelop the chorion, the processes of which fit into crypts in them.
The chorion is an outward skin which compasseth the child in the womb.
The chorion frondosum, together with the decidua serotina, gives rise to the placenta.
chorion cho·ri·on (kôr'ē-ŏn')
The outer membrane enclosing the embryo in reptiles, birds, and mammals. In placental mammals it contributes to the development of the placenta.