B. YI.] THE HISTORY OF ANIMALS. 143 



fluid, very brilliant in appearance, but without any hard 

 substance. This is the manner of the development of the 

 eyes and head. 



4. At the same period the viscera are visible, but the 

 stomach, and intestines, and the veins from the heart still 

 appear to extend towards the navel. From the navel a 

 vein appears to extend upon the membrane which encloses 

 the yolk, and the yolk itself is at this period fluid, and 

 more abundant than in its natural state. The other extends 

 to the membrane which encloses the whole membrane con- 

 taining the embryo, and the membrane of the yolk and the 

 fluid between them, and when the young birds have grown 

 a little more, part of the yolk goes to one end, and part to 

 the other, and between them is the fluid white ; but the 

 white is still below the lower part of the yolk, where it was 

 at first, but at the tenth day the white disappears, for it has 

 become small, viscid, thick, and rather yellow. 



5. This is the position of all the parts : the first and last 

 part adjoining the shell is the membrane of the egg, not the 

 membrane of the shell, but beneath this. This contains the 

 fluid white ; within this is the young bird, and a membrane 

 surrounding it, and separating it from the fluid ; beneath 

 the embryo is the yolk, to which one of the veins extends, 

 and the other to the white which encloses it. A membrane 

 containing a fluid resembling sanies encloses the whole, and 

 then another membrane which surrounds the embryo itself, 

 as I observed, and separates it from the fluid. Below this 

 the yolk, enclosed in another membrane, which is reached 

 by the umbilical cord Jrom the heart, and the great vein, so 

 that the embryo does not appear to be in either of the fluids. 



(3. About the twentieth day, if the hatching has been de- 

 layed beyond this period, the young bird is able to chirp 

 when moved externally, and if the shell is taken off, by this 

 time also it is downy. Tfce head is placed over the right leg 

 upon the side, and the wing is over the head. At this 

 period the chorion-like membrane is visible, which is united 

 with the lowest membrane of the shell, to which one of the 

 umbilical cords passes, and the young bird is complete. The 

 othei- chorion-like membrane is also visible, enclosing the 

 yoitf. To this the other umbilical cord extends. Both of 

 these cords are attached to the heart and the great vein. At 



