Seasonal Changes 



than starve, The herring-gull leads an agricultural life 

 during the summer, feeding upon any cereals he can find ; 

 in the winter, when grain is at a premium, he returns to 

 his diet of fish. 



The effects of light cannot altogether be dissociated 

 from the changes of the seasons. In winter the light is 

 much less intense than it is in summer, as every photog- 

 rapher knows. To attempt to trace the subtle changes 

 which take place owing to the reduced power of the 

 light in winter or its increase in summer would be beyond 

 the scope of our pages, but that light does affect animal 

 life we propose to show. The colouring of the common 

 sole or plaice or flounder is well known to everyone ; every 

 fish shop in the country can show samples with which we 

 may refresh our memories. Sand-coloured above, white 

 or nearly so below is a description, a rough description 

 certainly, which applies equally well to all three. 



On the upper surface of these flat fish a certain amount 

 of light falls, even in the ocean depths ; their under sides 

 for the greater part of the day lie on the sand, and are 

 not exposed to light, and that is the reason they are 

 white. Now early in its career not one of these flat fish 

 is flat. The statement sounds Irish, but it is none the less 

 true. The plaice, for example, when young is an ordinary- 

 looking fish, with one eye on either side, and it swims in 

 the usual fish manner. As it attains maturity it becomes 

 flattened, the side that is to be the lower grows paler and 

 paler in colour and, most remarkable change of all, the 

 eye that has appeared in danger of becoming useless 

 owing to its position below the fish gradually grows 

 round to the upper surface. 



But all this is by the way ; we are only concerned with 

 the effects of light. Experiments have been carried out 

 with flounders which, instead of being permitted to rest 

 upon the sand, as is their habit, have been illuminated 

 from below by means of mirrors, with the result that their 

 under sides assumed the duller hues of the upper sides. 



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