1832.] HABITS OF A DIODOX. 13 



the upper; and the fish, in consequence, floats with its back 

 downwards. Cuvier doubts whether the Diodon in this position 

 is able to swim; but not only can it thus move forward in a 

 straight line, but it can turn round to either side. This latter 

 movement is effected solely by the aid of the pectoral fins; the 

 tail being collapsed, and not used. From the body being buoyed 

 up with so much air, the branchial openings are out of water, 

 but a stream drawn in by the mouth constantly flows through 

 them. 



The fish, having remained in this distended state for a short 

 time, generally expelled the air and water with considerable 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 papilke, 

 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 Torres, 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 18th. We sailed from Bahia. A few days afterwards, 

 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 confervas, in bundles or rafts of from twenty 

 to sixty in each. Mr. Berkeley informs me that they are the same 

 species (Trichoclcsmiuin erythrteum) with that found over large 



