170 DR. BASIIFURD DEAN ox THE [Fel). 20, 



distance overland wrapped only in wet moss and water-weed — an 

 item which is here referred to since it indicates the aii'-breathing 

 capability of these fish (cf. O'Connor), At the time that the 

 present notes were prepai-ed both fish appeared to be in good 

 condition, although one of them was darker in colour and more 

 active than the other. 



The behaviour of the fish indicates that it is distinctly a bottom- 

 living for-m : it is sluggish in habit, its movements are deliberate, 

 and its general behaviour suggests that of an amphibian, e. g. 

 Necturus. As an example of the passiveness of the fish it may be 

 mentioned that when the fish was photographed it was thrust 

 about by the attendant until it was brought into the focus of the 

 camera, and it would usually bear this treatment without 

 excitement, behaving very much as would a Triton under similar 

 circumstances. A feature which one is soon apt to note is a 

 peculiar ventro-median ridge, which suggests that of Chlamydo- 

 selachus. From the behaviour of the fish and from numerous 

 experiments one is given the impression that the eyesight of 

 Ceratodus is poor, or, more accurately, that the reaction of the 

 fish to optical stimuli is remarkably slow. In this connection it 

 was noted that the eyes exhibited numei'ous and marked move- 

 ments, as though the fish were making an effort to see. From 

 this peculiarity I was led to inquire whether the fish could 

 see better by night than by day ; and this I was able to 

 accomplish, thanks to one of the many coui-tesies of Mr. R. I. 

 Pocock, the Sviperintendent of the Society's Gardens. From 

 these observations it was evident that the fish is far more active 

 by night than by day. It was found that the fish which remained 

 quiescent in a dark corner of the tank by day circled uneasily by 

 night. In one instance the fish was observed to pass twice around 

 the tank in the period of one minute ; and on several occasions the 

 fish broke the surface of the water boldly as thoiigh seeking to 

 escape. The movements of the fish on these occasions could be 

 adequately seen : for the observer standing in the dark was so 

 placed that he looked through the tank and saw the fishes 

 silhouetted against the skylight of a neighbouring room. There is 

 accordingly, it appears, but little doubt that Ceratodus is to be 

 regarded as largely nocturnal in habit. Especially was this evident 

 when a living Frog was chopped into the aquarium, for it was found 

 that its piesence was noted almost at once. 



In colour, one fish was much lightei-than the other — somewhat 

 greyish on the sides and back, and of a paler shade on the abdomen. 

 It is possible, by analogy with ganoids, that this specimen may 

 prove to be a female. The other specimen, possibly a male, is 

 much darker — blackish bottle-green, its surface slimy, with a 

 velvety bloom like the skin of a Salamander (Plate IX.). The fins 

 are darker in colour than the sides : the head is darker and greener. 

 The light colour on the ventral side of the head and on the lower 

 lip distinctly orange. Of the extreme colours should be noted the 

 darkness of the upper rim of the moitth and the ])aleness of the 



