PENNANT'S GLOBE- FISH. 45!) 



ing itself during this state of forced distension. But it is 

 while thus bloated and passive, at the mercy of the waves, 

 that this animal is really most secure ; for the numerous 

 spines with which the surface of the body is universally beset 

 are raised and erected by the stretching out of the skin, thus 

 presenting an armed front to the enemy on whatever side he 

 may venture to begin the attack." 



The following extract is derived from the very scientific and 

 interesting narrative by Mr. Charles Darwin of the Surveying 

 voyages of the Adventure and Beagle, vol. iii. page 13 : 

 " One day I was amused by watching the habits of a Diodon, 

 which was caught swimming near the shore. This fish is well 

 known to possess the singular power of distending itself into a 

 nearly spherical form. After having been taken out of water 

 for a short time, and then again immersed in it, a considerable 

 quantity both of water and air was absorbed by the mouth, 

 and perhaps likewise by the branchial apertures. This pro- 

 cess is effected by two methods ; the air is swallowed, and is 

 then forced into the cavity of the body, its return being 

 prevented by a muscular contraction which is externally 

 visible ; but the water, I observed, entered in a stream 

 through the mouth, which was wide open and motionless : this 

 latter action must, therefore, depend on suction. The skin 

 about the abdomen is much looser than that of the back ; 

 hence during the inflation, the lower surface becomes far 

 more distended than 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 likewise 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 were out of the water ; but a stream 

 drawn in by the mouth constantly flowed through them. 



* Dr. Roget. Bridgewater Treatise, vol. i. p. 433. 



