292 



EMBRYOLOGY. 



is generally slightly adherent to the vitellary membrane ; in 



such as have 

 been kept for 

 some time, it 

 is more de- 

 tached ; un- 

 der all circum- 

 stances it is 

 readily difflu- 

 ent, little con- 

 sistent. In 



A ^^ the centre it 



is somewhat 

 clearer and 

 more transpa- 

 rent than else- 

 where (fig. 

 319, e), and 

 allows the 

 germinal cu- 

 mulus, (cumu- 

 lusproligervA) 

 to be seen 



through it. This germinal cumulus is a loose whitish-yellow, 

 and somewhat conically formed granular layer, sunk in the 

 substance of the yolk ; betwixt it and the discus proliyerus, 

 or germinal disc, there is a minute interval, which is filled 

 with a fluid that appears to communicate with the canal of 

 the central cavity of the yolk.* 



@) 



Fig. 320. A, the unincubated yolk of the jack- 

 daw's egg (corvus corone) ; a, the vitellus ; b, b, 

 the chalazse ; c, the cicatricula. 



B, the cicatricula magnified. 



DETACHMENT OF THE OYUM EEOM THE OVAEY, AKD COM- 

 PLETION OF ITS FORMATION IN THE OVIDUCT. 



[ 481. The chorion, or outer covering of the ovum in the 

 ovary, coalesces with a layer of the ovarian stroma into a firm 

 capsule or theca (fig. 321, a). This capsule is surrounded ex- 

 ternally with cellular tissue and blood-vessels, and is particu- 

 larly thick in that part of its circumference towards the pedicle 



* In the foregoing description and terminology, Bae'r has been followed 

 as closely as possible. Vide his second volume, p. 10, et seq. 



