232 ANIMAL SKETCHES. CHAP. 



either deems it scarcely suited to her estate, or coquettishly 

 refuses to complete his happiness by laying therein her 

 eggs. Then is he wont to show himself an irascible little 

 fish, and chases her to the furthest corner of the tank. 



With the Thornie's other cousin, the marine fifteen- 

 spine stickleback, I cannot claim to be on intimate terms. 

 It is so long and thin as almost to deserve its trivial name 

 of sea-adder. Its small rnouth lies at the end of an elon- 

 gated snout ; and the colouring varies from reddish brown 

 to dark green. Like the Thornies, it is a nest-builder, 

 using for this purpose seaweed or coralline, which it binds 

 together with elastic silk-like threads. How these silken 

 threads are produced has long been a matter of uncertainty. 

 But quite recently Professor Mobius has shown that they 

 are secreted by the kidneys as a mucous material, which 

 hardens by exposure to the water. 



But it is high time to return to my rosy-cheeked, blue- 

 eyed little Thornie whom we left awhile ago, and in whose 

 nest had been deposited a number of small yellow eggs. 

 Most carefully did he watch over the nest, continually 

 returning to it, and fanning with his pectoral fins a current 

 of water over the developing ova that these might not 

 perish for lack of vitalizing oxygen. In about three weeks 

 or somewhat longer he was rewarded for his assiduous care 

 and attention by becoming the proud father of a healthy 

 brood of minute transparent fishes. When I first noticed 

 them darting here and there about the tank, they must 

 have been hatched two or three days. The father did not 

 as a rule, seem to take very much notice of them. But 

 when I placed their mother in the tank, she at once showed 

 her maternal fondness by swallowing as many as she could 

 catch. The male, however, soon put a stop to this by 

 chasing her up to the surface ; nor would he allow her to 

 descend to the lower stratum of water in which the little 



