BRITISH FRESH-WATER FISHES 



produce sufficient eggs to satisfy his desires. After the 

 first batch are laid, a second female is invited to add to 

 the number, and this operation is repeated by others 

 several times. If the nest is damaged the male will 

 undertake the necessary repairs, and he will aerate the 

 water by quick movements of his fins. The materials 

 composing the nest are fastened together by a sticky 

 substance with which this species is provided. 



It should be mentioned that rough-tailed and smooth- 

 tailed forms of Three- Spined Sticklebacks occur in 

 Britain, but the latter are mostly found in inland waters, 

 and there are also intermediate forms. These, however, 

 need not detain us. 



Ten-Spined Sticklehack.—Pygosteuspungitius (Fig. 59). 

 This well-distributed species is at once distinguished by 

 the larger number of short sharp spines along the back. 

 Although called Ten-Spined, the back spines may consist 



Ten-spinexi Stickle-back Vig 59 



of from 7 to 12, and there are others below as in the 



species last under review. This is smaller than Gastro- 



stens aculeatiis, rarely exceeding 3 inches in length. 



In its general life-history this species closely resembles its 



lesser-spined cousin, but it is more of a fresh-water 



inhabitant. Tt is dark greenish, dotted with black. 

 106 



