THE AUSTRALIAN LUNG-FISH. 611 



The mouth itself showed no noticeable movement of opening 

 or closing ; it was indeed hardly open, the gape scarcely more than 

 g inch. During the later observations, the mouth was seen 

 slightly to open and close; its maximum gape noted (measured 

 close to the glass) was | inch, its minimum ^ inch. The opening 

 of the mouth was here doubtless correlated with the higher 

 temperature of the water and the more rapid respiratory 

 movements. In general, however, the mouth margin was 

 almost motionless, the fish breathing through the nostrils. 



In the matter of breathing air at the surface, Ceratodus shows 

 greater variability than earlier noted. On one occasion over 

 seventy minutes elapsed without either fish coming to the surface. 



Feeding. — Little was added to the former notes. The only 

 detail suggests that minute food, in the form of algse together 

 with vegetable debris, forms a part of the normal diet. It was 

 observed that the fishes would " nose " about in corners and suck 

 in this finer material. In the process little pebbles would some- 

 times be taken in and retained for a few moments, then rejected — 

 the process several times repeated, in a fashion which suggested 

 that the stones thus mouthed yielded food sought for by the 

 fish. It was noted in this connection that the stones in the 

 aquarium were in many cases well coloured with algse. 



Text-fig. 85. 



Pectoral fin of Ceratodus forsteri, showing regenerating margin. 



Movements, — The writer's preceding paper gave a number of 

 figures showing characteristic movements of Ceratodus. The 

 only addition to this series would be a variant of the fig. 11 

 there given ; the right hand pectoral remained in its resting 

 position (as in fig. 14) ; the left, however, was suddenly twitched 

 up over the back several times (as in fig. 11), but in this case 

 brushed close to the body, giving the observer the amusing 

 impression that the fish was thoughtfully rubbing its head. The 

 habit was curiously unlike that of a fish ; it suggested rather 

 the movement of a tetrapod ; and a very similar movement is 

 known in urodeles. 



Regeneration. — The larger (dark coloured) specimen had suffered 

 an injury to the left ventral fin ; a portion of it near the tip 



