EVOLUTION OF THE CHICK. 



153 



may be remarked. The spinal marrow, divided into 

 two parts, is extended along* the trunk ; the liver, 

 previously whitish, becomes of a darker dusky colour. 

 It is now seven lines* in length. 



An Egg as it appears six days after incubation, with a magnified view of 

 the Chick. 



On the seventh day it is easy to distinguish the 

 bill ; and the skin, with the germs of the feathers, 

 becomes obvious. 



On the eighth day the brain, the wings, thighs, 

 and legs, have taken nearly their ultimate form ; but, 

 according to Scarpa, are still soft, flexible, and pel- 

 lucid f. The two ventricles of the heart also appear 

 like two bubbles, contiguous and joined above to the 

 substance of the auricles ; while two successive mo- 

 tions are now observed in them, as well as in the 

 auricles, which resemble two separate hearts. 



* A line is the twelfth part of a French, or rather less than 

 the eleventh of an English inch. 



t De Penit. Ossium Structura Comment. 4to. Lips, 1799. 



