1046 FRESH-WATER BIOLOGY 



the young began to swim and became scattered, the parents con- 

 tinued to suck them in and mouth them, and, as subsequently 

 developed, did not always blow them out. 



"An interesting habit of the parents, more especially the male, 

 observed during the first few days after hatching, was the mixing and 

 stirring of the masses of young by means of the barbels. With the 

 chin on the bottom, the old fish approached the corners where the 

 fishes were banked, and with the barbels all directed forward and 

 flexed where they touched the bottom, thoroughly agitated the 

 mass of fry, bringing the deepest individuals to the surface. This 

 act was usually repeated several times in quick succession. The 

 care of the young may be said to have ceased when they began to 

 swim freely, although both parents continued to show solicitude 

 when the attendant approached the aquarium from the rear." 



In contrast to the nest-building habits are the habits of those fishes 

 seeking a definite sort of locality where to deposit their eggs. The 

 dace (Semotilus), stone roller (Campostoma) , and rainbow darter 

 (Ethesostoma caeruleum) select gravelly bottom on shallow riffles 

 above a pool. The habits of the darter have recently been made 

 the subject of exhaustive study by Miss Cora D. Reeves. 1 These 

 fishes spawn when the temperature reaches about 66 F. The 

 males select holdings which they guard and from which they drive 

 rival males by a display of color and by blows delivered with head 

 and tail. The female buries herself partly in the gravel, the male 

 taking a position over her, other males crowding in. A few eggs 

 and milt are extruded at a time and the spawning act oft repeated. 

 The eggs are adhesive and stick to the gravel. 



The adaptation to currents in fresh water thus consists in various 

 devices to anchor the eggs. The adaptation against sediment is 

 found in the guarding and fanning habit of the male, the deposit 

 of eggs to the lower surface of rocks or boards and on riffles, and 

 the suspension of eggs from water weeds. To these groups of 

 more or less adaptive habits we must add the peculiar brooding 

 habits of some catfishes, Cichlids, and the blind fishes, and Cyprin- 

 odonts. Some of the South American catfishes have the habit of 

 carrying their eggs in the mouth. Some of them, Aspredo, carry 



1 Biol. Bull., 14 : 35. 



