334 DOMESTICATED TROUT. 



carotid being more active than the left, and the left jugu- 

 lar more active than the right. The aortic arch at the 

 right is also more powerful. Intestinal arteries form. The 

 liver develops more and more to the detriment of the yolk 

 circulation. The little drops of oil unite in one great drop. 

 The buccal intestine enters into communication with the 

 branchial cavity. 



From the forty-first to the sixtieth day the embryo be- 

 comes ready to hatch. The nose draws insensibly near 

 the extremity of the head. The cartilaginous bases of 

 the head form from the thick blastema of the base of the 

 cranium. In the eye the cornea and the sclerotic separate 

 from the tissues of the choroid. The ear approaches the 

 eye. The interior parts of the eye completely develop. 

 The heart takes a horizontal position in consequence of 

 the proximity of the yolk and the body, a proximity 

 which itself depends upon the disappearance of the peri- 

 cardial sac and the abdominal sac of the epidermoidal 

 membrane. The yolk disappears from sight. Peristaltic 

 motions and very decided movements of mastication can 

 be perceived in the intestine. The mouth, situated be- 

 tween the eyes, is transversal. The embryonic odd fin 

 shows cavities in the places where it is designed to be 

 absorbed. The yolk circulation disappears, that of the 

 liver or the circulation of the portal system is entirely 

 established. The sixth branchial arch, or the pharyngian 

 arch, receives a vascular arch. The hyoidian arch has 

 disappeared. The head contracts as the formation of the 

 cartilages progresses. The vertebrae become cartilaginous. 

 The muscular fibres take transverse striae. 



Immediately after the spawning the essential modifica- 

 tions are as follows : The yolk is little by little completely 

 absorbed. The oil drop lasts the longest, but it also finally 

 disappears. The yolk circulation passes entirely to the 

 liver, and there completes the circulation of the portal 



