Fish Study 169 



If large eyes count for beauty, then the stickleback deserves "the 

 apple," for its eyes are not only large but gemlike, with a broad iris of 

 golden brown around the black pupil. I am convinced that the stickle- 

 back has a keener vision than most fish; it can move its eyes backward 

 and forward rapidly and alertly. The mouth opens almost upward and 

 is a wicked little mouth, both in appearance and action. 



When swimming, the stickleback darts about rapidly, its dorsal and 

 anal fins extended, its spines all abristle, its tail lashing the water with 

 strong strokes and the pectorals flying so fast that they make a blur; the 

 ventral fins are rarely extended, in fact they are nothing but two little 

 spines. When the fish wishes to lift itself through the water it seems to 

 depend entirely upon its pectoral fins and these are also used for balanc- 

 ing. Its favorite position is hanging motionless among the pond weeds, 

 with the tail, the dorsal and ventral fins partially closed; it usually rests 

 upon the pectoral fins which are braced against some stem ; in one case I 

 saw the ventrals and pectorals used together to clasp a stem and hold the 

 fish in place. In moving backward the pectorals do the work, with a 

 little beckoning motion of the tail occasionally. When resting upon the 

 bottom of the aquarium, it closes its fins and makes itself quite incon- 

 spicuous. It can dig with much power accomplishing this by a comical 

 augerlike motion; it plunges head first into the gravel and then by 

 twisting the body and tail around and around, it soon forms a hiding 

 place. 



But it is as a house builder and father and home protector -that the 

 stickleback shines. In the early spring he builds him a nest made from 

 the fine green alga? called frog-spittle. This would seem a too delicate 

 material for the house construction, but he is a clever builder. He fastens 

 his filmy walls to some stems of reed or grass, using as a platform 

 a supporting stem; the ones which I have especially studied were fastened 

 to grass stems. The stickleback has a little cement plant of his own, sup- 

 posed to be situated in the kidneys, which at this time of year secrete the 

 glue for building purposes. The glue is waterproof. It is spun out in 

 fine threads or in filmy masses through an opening near the anal fin. 

 One species weights his platform with sand which he scoops up from the 

 bottom, but I cannot detect that our brook stickleback does this. In his 

 case, home is his sphere literally, for he builds a spherical house about the 

 size of a glass marble, three-quarters of an inch in diameter; it is a hollow 

 sphere and he cements the inside walls so as to hold them back and give 

 room, and he finishes his pretty structure with a circular door at the side. 

 When finished, the nest is like a bubble, made of threads of down and yet 

 it holds together strongly. 



In the case of the best known species, the male, as soon as he has 

 finished his bower to his satisfaction, goes a-wooing; he selects some lady 

 stickleback, and in his own way tells her of the beautiful nest he has made 

 and convinces her of his ability to take care of a family. He certainly has 

 fetching ways for he soon conducts her to his home. She enters the nest 

 through the little circular door, lays her eggs within it, and then being a 

 flighty creature, she sheds responsibilities and flits off care free. He 

 follows her into the nest, scatters the fertilizing milt over the eggs and 

 then starts off again and rolls his golden eyes on some other lady stickle- 

 back and invites her also to his home; she comes without any jealousy 

 because she was not first choice, and she also enters the nest and lays her 



