156 BRITISH FISHERIES 



(Centronotus)) again, the female forms the extruded 

 eggs into a ball, and these are surrounded by 

 the coiled body of the fish. The lump-sucker 

 (Cyclopterus) of British seas deposits its eggs in 

 one large mass in a rock pool, and thereafter the 

 female indicates no concern for her progeny. The 

 male, however, keeps guard over the spawn, and 

 causes a current of water to flow over and through 

 the mass of eggs by gentle movements of his tail. 

 This paternal instinct is often fatal to the unhappy 

 sire, who is sometimes left stranded by the receding 

 tide, and either captured by small boys or destroyed 

 by crows or other predaceous birds. The fifteen- 

 spined stickleback (Gasterosteus spinachia) builds a 

 nest constructed of sea-weeds cemented together 

 by mucus. 1 It is the male in this case which is 

 the architect ; the female takes no part in the 

 process, but, on the other hand, seeks to devour 

 the eggs contained in the nest, and is only pre- 

 vented from doing so by the efforts of the male. 



There are, however, exceptions. The almost 

 invariable rule (except in the dog-fishes, sharks, and 

 rays) is for the female to shed her eggs into the 

 sea. At the same time the male, who is " standing 

 by," sheds the " milt " or spermatozoa, which then 

 mix with the eggs and impregnate them. With 

 these acts the parents cease to give any attention 

 to the spawn. 



1 See the beautiful figure of the nest of the stickleback in 

 M'Intosh and Masterman's British Marine Food Fishes. 



