76 BRITISH FRESH-WATER FISHES 



in colour than the female, and in both sexes the iris is 

 red. The fish possesses no air-bladder, and the stomach 

 is a capacious round sac, lined internally with a black 

 pigment. 



The species is very widely distributed, very few water- 

 sheds being without it between Britain and Siberia, France and 

 Northern Asia, where its place is taken by other 



Distribution. . j 



species m that region and North America. But the 

 miller's thumb is so scarce in Irish waters that its very 

 existence has been denied, and it has not been recorded from 

 Spain or Greece. Personally, I have never seen this species 

 in Scotland. 



In habit, the miller's thumb is the reverse of obtrusive ; 

 its custom is to lie under a stone, with the gaping mouth ready 

 to seize any passing insect. Izaak Walton says that 

 " in very hot days he will lie a long time very still, 

 and sun himself, and will be easy to be seen upon any flat stone 

 or gravel," which reads like a piece of genuine observation. 

 Other writers have repeated this statement, but whether 

 founded upon what they have seen or only upon what they 

 have read, the present deponent sayeth not. Inasmuch as I 

 have not happened to witness this habit in the miller's thumb, 

 albeit I have wasted more time by the waterside than it is 

 creditable to record, I am not qualified either to confirm or 

 deny this behaviour of the fish in question. Usually its 

 leading motive seems to be keeping out of sight, as if conscious 

 of its own ugliness. 



The spawning takes place early in spring, when the female 

 deposits bunches of rosy-tinted ova in what is called by 

 courtesy a nest, but which is nothing more than a natural 

 depression in the sand or gravel, or one worked out by herself. 

 Having performed this part of the domestic economy, it is 

 said that the prolific mother retires from the nest, and leaves it 

 to the protection of her mate, who watches it carefully for four 

 or five weeks, and does his best to repel the attacks of 



