S832.J A SHARK'S CURIOUS DEATH. 27 



The fish, having remained in this distended state for a 

 short time, generally expelled the air and water with con- 

 siderable force from the branchial apertures and mouth. 

 It could emit, at will, a certain portion of the water ; and 

 it appears, therefore, probable that this fluid is taken in 

 partly for the sake of regulating its specific gravity. This 

 Diodon possessed several means of defence. It could give 

 a severe bite, and could eject water from its mouth to 

 some distance, at the same time making a curious noise by 

 the movement of its jaws. By the inflation of its body, the 

 papillae, with which the skin is covered, become erect and 

 pointed. But the most curious circumstance is, that it 

 secretes from the skin of its belly, when handled, a most 

 beautiful carmine-red fibrous matter, which stains ivory 

 and paper in so permanent a manner, that the tint is 

 retained with all its brightness to the present day : I am 

 quite ignorant of the nature and use of this secretion. I 

 have heard from Dr. Allan of Forres, that he has frequently 

 found a Diodon, floating alive and distended, in the stomach 

 of the shark ; and that on several occasions he has known 

 it eat its way, not only through the coats of the stomach, 

 but through the sides of the monster, which has thus been 

 killed. Who would ever have imagined that a little soft 

 fish could have destroyed the great and savage shark ? 



March iZth. — We sailed from Bahia. A few days after- 

 wards, when not far distant from the Abrolhos Islets, my 

 attention was called to a reddish-brown appearance in the 

 sea. The whole surface of the water, as it appeared under 

 a weak lens, seemed as if covered by chopped bits of hay, 

 with their ends jagged. These are minute cylindrical 

 confervae, in bundles or rafts of from twenty to sixty in each. 

 Mr. Berkeley informs me that they are the same species 

 {Trichodesmium erythrceum) with that found over large 

 spaces in the Red Sea, and whence its name of Red Sea is 

 derived.* Their numbers must be infinite : the ship passed 

 through several bands of them, one of which was about ten 

 yards wide, and, judging from the mud-like colour of the 

 water, at least two and a half miles long. In almost every 

 long voyage some account is given of these confervse. They 

 appear especially common in the sea near Australia ; and 

 off Cape Leeuwin I found an allied, but smaller and 



• M. Montajfne, in "Comptes Rendui," etc., Juillet, 1844; and " Annal, dea 

 Scienc. Nat.," Dec. 1R44. 



