154 THE BRITISH NATURE BOOK 



The Pope, or RUFFE (Acerina cernua), is common in lakes and slow rivers. 

 It is not more than 6 inches in length, and has the spiny fins of its family. 

 Instead of the dark bands of the perch it is mottled and spotted with brown, 

 whilst it possesses only one dorsal fin. 



The Bullhead, or MILLER'S THUMB (Coitus Gobio), belongs to a family repre- 

 sented in salt water by the familiar FATHER LASHER (C. Scorpio). To most 

 people this is rather a repulsive little fish, owing to its ugly large head, 

 its slippery skin, and the spines on its crown. But it has a beauty of its own 

 when examined in detail, and makes a quaint inhabitant of an aquarium. 

 In addition, though it is so small, its flesh is delicate, and when boiled is reddish 

 like a Salmon's. It buries its spawn in a hole which the female makes with 

 her tail, and over this nest the male keeps a courageous guard. 



STICKLEBACKS. 



With this genus we deal with a family of fishes in which the dorsal fin 

 has been replaced by strong spines, which vary in number according to the 

 different species. They are small fish, and the male is brightly coloured, 

 especially during the breeding season. One of our British species (the 

 FIFTEEN-SPINED STICKLEBACK) is marine; the other two are found in fresh 

 or brackish water. 



1. Three-spined Stickleback (Gasterosteus aculeatus), which by-the-bye is 

 sometimes four-spined, is the commonest, and is known to most boys by its 

 nickname of " Soldier," from its bright red colouring during the breeding season. 

 The remarkably interesting story of the Stickleback has been told so often 

 that it may be mentioned with brevity here. The male makes a nest of grass 

 and stems or, in salt water, of seaweeds cemented firmly together into a 

 barrel shape, with openings at front and back. When completed, the male 

 sallies forth to find a wife, and endeavours to coax her inside to deposit her 

 eggs. When she has finished her task, and the eggs are fertilized, the male 

 induces other females to enter, until the nest is filled, when he sets himself to 

 guard it with jealous vigilance, allowing no other fish to come within reach 

 of it. Even when the ova are hatched his labours do not cease, but are 

 increased by the difficulty of keeping the " babies " in the shelter of the nest 

 until they are big enough to look after themselves. 



The Three-spined Stickleback is covered with plates instead of scales, 

 and is greenish, silver, and brown, except in the male during the breeding 

 season. 



2. The Ten-spined Stickleback (G. pungitius) possesses no plates on the 

 sides of the body ; and the male, during the breeding season, becomes a deep 

 black. 



3. The Fifteen-spilled Stickleback (G. spinachia) is olive-brown and white 

 in colour, and may be identified not only by the number of spines but by the 

 long body and snout and large size. On the Continent it is both a marine 



