206 THE OCEAN. 



bers of the heart are present, but there is a commu- 

 nication open between the left and right ventricles ; 

 and the aorta and pulmonary artery both originate 

 fi'om the rigid ventricle. In consequence, a part 

 only of the blood is sent thence to the lungs, which, 

 returning through the left auricle and ventricle, is 

 thrown into the right ventricle, and mixed with that 

 which is just brought from the body ; the mixed 

 blood being partly returned to the body through the 

 aorta, and partly sent to the lungs. But this is the 

 course only when the animal is breathing ; and as a 

 large part of its life is passed under water, this con- 

 trivance enables the circulation to go on under cir- 

 cumstances when breathing necessarily ceases. For 

 if no air enters the lungs, the blood cannot pass 

 through them ; therefore, when under water, the 

 blood passing through the right auricle and ventricle 

 is immediately sent by the aorta into the body with- 

 out any exposure to the air. Of course, as the blood 

 thus unrenewed would become more and more im- 

 pure, this could not proceed very long without loss of 

 life, and hence there is a limit to the period during 

 which the breathing may be suspended, when the 

 animal must come to the surface or die. 



Many of the fishes of these seas partake of the 

 brilliancy of colour with which the birds and insects 

 of the same sunny region are so lavishly adorned. 

 I have seen some of great beauty readily captured 

 with a hook from the deck of a vessel in shallow 

 water; the Yellow-fin has its body marked with 

 longitudinal bands of delicate pink and yellow alter- 

 nately ; the fins are bright yellow, and the tail fine 



