162 Part III. — Twenty-second Annual Report 



with the codlings and whitings, and most of them died at one time or 

 other during the course of the experiments. They did not appear to 

 make themselves at home, so to speak, as the codlings and the whitings 

 did, and they were obviously, under the conditions of the experiment, 

 more stupid fish. When the fish were fed the chopped mussels were 

 dropped gradually into the water, and the moment the fragments began 

 to sink the whitings and codlings rushed at them and, even when replete 

 of a previous meal, took them into their mouths and put them out again, 

 or smelt them ; their movements were thoroughly purposive in relation to 

 the food. The haddocks, on the other hand, excited by the commotion, 

 or it may be by the odour of the mussels also, rushed aimlessly about at 

 such times, snapping at the other fishes and missing the fragments 

 although often quite near them and themselves quite hungry. The 

 haddocks, it was also noticed, kept closer to the bottom, and looked for 

 their food there rather than in the course of descent through the water.* 



The fact has to be taken into account, because, although food was 

 supplied abundantly, it is pretty certain that the haddocks, as a rule, got 

 only what the others left. 



It is probable also that the haddocks suffered more than the other 

 fishes from not getting a more natural food. With reference to tempera- 

 ture they were also more sensitive than the others. When the water got 

 comparatively warm, say about 60° F., the haddocks first showed signs of 

 distress and went round the tank near the top gasping or tried to jump 

 out, and I attribute the deaths of most of the haddocks to this cause. 

 On one occasion I transferred a haddock of 19"9cm. from water of a tem- 

 perature of 7*4 C. (45-3 F.) to water of 15 C. (59 F.) and it was killed in 

 about two minutes, as if it had been poisoned ; it rapidly became paralysed, 

 swayed about a few moments and then sank with its mouth open. A 

 small whiting (15*0cm.) transferred at the same time appeared to be doing 

 well, but was found dead the next morning. The haddocks, moreover, were 

 observed to seek the coolest parts of the hot-water tank, while, unless 

 when the temperature was very high, the whitings and codlings in that tank 

 seemed to enjoy themselves and were active and alert. It may be said 

 that at first the hot water was run in on the top, but it was found that 

 there was a difference of two or three degrees under these circumstances 

 between the surface and bottom water ; thereafter it was carried towards 

 the bottom by a pipe, arrangements being made for air passing in with the 

 water at the same time and thus the temperature was nearly equalised. 



During the cold weather in winter a great contrast was shown between 

 the fishes in the warm tanks and those in the tanks where the temperature 

 was low, the difference in temperature being about 9 C. In the 

 former they moved about actively and were keen and alert and, if the ex- 

 pression maybe used, were happy; in the cold water tanks the fish, on the 

 other baud, were sluggish, remaining a long time at one spot, and gently 

 swaying their fins : the movement and activity in the one tank offered a 

 marked contrast to the comparative lifelessness in the adjoining tank. It 

 has already been said that the fishes in the warm water had a far better 

 appetite than those in the cold water and ate much more ; it was, more- 

 over, observed that at times when the temperature was low, down to about 

 3-8 C, or a little above the freezing point of fresh water, the fishes in 

 these tanks gave up feeding altogether, while in the adjoining heated tanks 

 the fish were fighting eagerly for the food. In the former at such times the 

 mussels would be left untouched at the bottom of the tank. This confirms 



* It may be here stated that the haddocks, as a rule, swam nearer the bottom than the 

 codlings or the whitings, and this was especially noticeable at first when the fishes were 

 introduced into the tanks. While the haddocks grovelled about the bottom, the 

 whitings were dispersed upwards to near the top of the tank. The observation as to the 

 difference in habit may have reference to the fact that whitings and codlings are caught in 

 far greater proportions than haddocks by the otter-trawl compared with the beam-trawl 



