Scientific Intelligence — Zoology. 429 



of birds truly songsters ; those of tho New World abound principally 

 in birds with a loud and clear voice, but of little variety, and resound 

 with cries rather than songs. Besides these two widely extended 

 forms, there are many other laryngical organizations of a more espe- 

 cial nature ; the most complicated is that of the parrot tribe. 



M. Muller's memoir contains numerous facts of detail, and like- 

 wise plates explanatory of all the forms described. 



10. Physiological Remarks on the Statics of Fishes. By J oh. 

 Muller. — Like all other animals, fishes have a very delicate sense 

 of the equilibrial position of their bodies. They endeavour to coun- 

 teract all change in this position, by means of movements partly 

 voluntary and partly instinctive. These latter appear in a very re- 

 markable manner in the eyes ; and they are so constant and evident 

 in fishes while alive, that their absence is sufficient to indicate the 

 death of the animal. 



The equilibrium of tho body of a fish in the water is independent 

 of the swimming bladder; that organ may even be injurious to it. 

 The equilibrium of the fish, its horizontal position, with the back 

 upwards, depends solely on tho action of tho fins, and principally 

 that of the vertical fins. 



Tho swimming bladder may enable a fish to increase or diminish 

 its specific gravity. By compressing the air contained in it, the fish 

 descends in the water; it rises by relaxing the muscles which pro- 

 duced this compression. Besides, the fish may continue in the deep 

 parts of the water in consequence of the mere pressure of the column 

 of water on the air contained in the bladder. 



By compressing more or less the posterior or anterior portion of 

 the bladder, the animal, at pleasure, can make tho anterior or poste- 

 rior half of its body lighter ; it can also assume an oblique position, 

 which permits an ascending or descending movement in tho. water. 

 The arrangement of the swimming bladder in some fishes may fa- 

 vour this action. The Cyprinoides and Characins have two bladders, 

 one before the other, and communicating with each other by a nar- 

 row neck. The anterior bladder is very elastic, while tho posterior 

 is very slightly so ; accordingly, in proportion as the fish ascends in 

 the water, the anterior and more elastic bladder must increase in size 

 considerably, and tend to keep the head upwards, while the contrary 

 must take place when the fish descends. 



1 1 . Red Colour of the blood in the Planorhis imhricatus. By M. 

 de Quatrefages. — By observing the Planorhis imhricatus by means 

 of a transparency, M. de Quatrefages has ascertained that this little 

 mollusc, which is very common in the fresh water around Paris, pos- 

 sesses blood of a red wine colour. Under a faint magnifier, tho 

 liquid may bo seen filling the cavities of the pericardium and ven- 

 tricles, and by its motions colouring pretty distinctly the whole gene- 

 ral caviiy of the body on its lower surface. M. de Quatrefages 

 could not perceive distinct globules in this liquid. Other Planorbes, 



