310 LIFE BY THE SEASHORE. 



have received less attention than the three-spined form. It 

 does not appear to extend into fresh water, and is most 

 abundant in pools containing much weed and stones, but 

 I have also found it in sandy places. It will be noted that 

 it is the male which makes the nest, and watches over the 

 eggs, just as it is the male lump-sucker which watches over 

 the eggs. It is true generally of bony fishes that where 

 there is any evidence of parental care, it is the male parent 

 which takes on this duty. The same is true of Amphibians 

 frogs, toads, newts, and their allies while among 

 mammals the care of the young usually falls to the mother 

 alone. 



In addition to the fifteen-spined stickleblack, the three- 

 spined form (Gasterosteus acideatus] does occasionally occur 

 in rock pools, though typically a fresh-water form. It 

 occurs not infrequently in brackish pools just at high-tide 

 mark, especially those in the vicinity of fresh-water streams. 

 In such pools, also, the nests may at times be found, but 

 they are too well known to need further description. The 

 three-spined stickleback is hardly so pretty a fish as the 

 fifteen-spined form, for it has a more typical fish-like 

 shape, without the long snout of the fifteen-spined form, 

 and with three, or occasionally three or four, spines on the 

 back instead of fifteen. Usually the fish are not more than 

 two to three inches in length, but they are excessively 

 pugnacious, not only fighting furiously with each other, but 

 never hesitating to attack fish much larger than themselves. 

 In such combats the strong spines, which they can use very 

 effectively, form very powerful weapons, while the strong 

 plates at the sides of the body form an efficient defence 

 against the attacks of other fish. In the breeding season 

 the males especially are of a brilliant orange-red beneath, 

 the colours both there and in the other parts of the body 

 varying in intensity according to the emotions of the fish, 

 being brightest after victory, palest after defeat, or when 

 the fish are under the influence of alarm. The tolerance of 

 either fresh or salt water is remarkable, especially as there 

 is no regular seasonal alternation between the two as in 

 salmon or some other fish. The extraordinary variability 

 must be associated with the power of changing the environ- 

 ment ; but while certain varieties seem to be better adapted 



