106 BRAIN AND BODY OF FISH 



the same family living on a very similar diet and yet presenting a 

 very different method of hunting their prey. The general aspect 

 of Phycis is that of a typical cod, and a further examination proves 

 that it has the characteristics of this family in the details of its jaws 

 and dentition, its fins, scales and so on. 



Its dentition is very similar to that of gadus morrhua with a 

 well-marked V-shaped area on the vomer and this indicates a 

 shell-fish diet, so that it is not surprising that the German name for 

 this fish is " shell-fish," which, it will be remembered, is also given to 

 our haddock. The head is shorter and broader than that of the 

 haddock and suggests that of a cat ; this is due apparently to the 

 large space occupied by the otohths, which are exceptionally large. 

 There is a small barbel under the chin, and on either side is a long 

 finger-hke feeler which is prolonged distaUy by two filaments ; 

 this is merely a modified fin-ray and does not bear any taste-buds. 

 These also recall the cat and its whiskers. But when in the course 

 of removing the roof of the skull to expose the brain, the firm grasp 

 on the trunk caused the animal to purr, the name of cat-fish seemed 

 most appropriate. 



On opening the abdomen to investigate the cause of this strange 

 noise, to my astonishment I found that the swim-bladder was not 

 attached to the dorsal wall of the cavity as in most cods, but that 

 there was a triple-expansion gas-bag loosely attached, except at 

 its anterior end. The three compartments of the sac were separated 

 by narrow constrictions ; the jJosterior compartment was the largest, 

 of the size of the posterior sac of a Cyprinoid of similar weight. It 

 had a tough external coat and a thin internal coat. The middle 

 division was smaller and lying in the front part its wall contained 

 two small retia mirabilia, vascular bodies covered with a specialised 

 epithehum, which enables the animal to secrete gas ; the anterior 

 sac was partially divided into two so as to produce two auricles on 

 either side, which were capped by a thick mass of muscular tissue. 

 At the base of each auricle there was also a small rete mirabile. 



It was the pressure on this sac that presumably caused the 

 queer noise which was heard when I pressed the body of the fish, 

 and there can be little doubt that the contraction of the muscles 

 of the auricles of the anterior chamber are able to produce sound 

 by diiving gas from one sac to the other ; in fact, act as a kind of 

 bag-pipe. How strange it seems to find a sound producing organ in 

 a cod when the cod of our waters has only an air-bladder which 

 divides anteriorly into a pair of caecal prolongations which extend 

 forwards to the head and are often ciu-iously coiled. This condition 

 of the swim-bladder is associated with the auditory organ. 



