52 THE FKESH-WA'I'Kl; I'lSHKS ()K ET'llOPE. 



the ovaries in the female, has a wide external aperture near to the pear- 

 shajjed urinary bladder, opening- throug-h the uro-g-enital papilla. 



When young", individuals are eharaeterised by having very conspicuons 

 pores aljove and below the lateral line, as well as by the undivided rays 

 of the pectoral fin already mentioned. The male is usually the darker fish, 

 has a rather broader head, and long'er uro-g-enital papilla. In the female 

 the ovaries become excessively enlarged at spawning-time. The fish attains 

 a length of five or six inches. 



This species is found in the smallest streams wherever the water is clear. 

 [t is common in all parts of Scotlantl, but so rare in Ireland that its existence 

 in Derry has been more than once tpiestioned. Bhmchard enumerates locali- 

 ties for it in all parts of France, Fatio finds it in Switzerland up to a 

 height of between 6,000 and 7,0UU feet, Heckel and Kner meet with it 

 not only in the Danube and its tributaries, but in the small Austrian 

 lakes; and some varieties of it are found in the Ilartz. It is found in 

 Scandinavia, and may sometimes descend the streams into the Baltic. Pro- 

 fessor Canestrini enumerates many localities in the north of Italy, where 

 it is found, 1)ut it has not been recorded from Spain or Greece. It is common 

 in Siberia. 



The River Bullhead, or IMiller's Thumb, is an active, voracious fish of 

 solitary habit, which lies concealed under stones, and feeds on insects, insect 

 larvae, and the fry of young fishes ; and females have been found with their 

 own eggs and fry in the stomach. 



When attacked by other fishes, or by carnivorous birds, it defends itself 

 by exi)anding the pectoral fins and the operculum, so that the opercular 

 spine becomes a formidable weapon, which has often proved fatal to birds 

 which have attempted this armoured morsel. 



It spawns in March and April, when the females deposit the eggs 

 under stones, or excavate special depressions in which they may be placed. 



Experienced fishermen narrate^ how the male, having discovered a suitable 

 depression between stones, valiantly defends it against other males who would 

 dispossess him of his holding; and a Cottus is often captured holding in its 

 mouth the head of an antagonist which he is unable to swallow. If a female 

 comes by she is welcomed to the retreat which the male Goby has secured, 

 and after being installed she deposits her eggs. These are about two 

 millimetres in diameter, of a pinkish colour, are commonly connected like 

 bunches of grapes, and occasionally adorn the nuptial chamber by being 

 suspended from the roof. The mass of ova may cover an area of an inch 

 and a half of ground, and they have been compared in aspect to frog's spawn. 

 The number of eggs varies with the age of the individual. In the nest of 



