PROPAGATION 



59 



gravel. One may often see in breeding pords places that have 

 been thus tested. They may be no more than four or five 

 inches across, or may be irregular linear patches several feet 

 long, and in such spots the gravel is exposed, while all about 

 them it is hidden under a smooth layer of sediment. When 

 he has found a suitable place the male takes a vertical positicn 

 in the water, head up, and by a powerful sweeping movement 

 of the tail he removes from an area two or three feet across 

 the sediment which covers the gravel. When this occurs in 

 a stream, the sediment, car- 

 ried down by the current, 

 settles to the bottom below 

 the nest. In ponds where 

 there is no current the sedi- 

 ment is not carried down and 

 the water over the nest be- 

 comes consequently so much 

 rolled during the sweeping 

 that the fish frequently is 

 forced to leave the nest until 

 the water has become clear 

 again. The sweeping clean 

 of the gravel is the first stage white Cedar 



in the building. The nest is 



then said to be "cleaned up," but is not yet completed. 

 The fish next stands on its head, roots over the gravel, more 

 particularly at the centre of the nest, and then resrmes 

 sweeping with his tail. He thus alternately roots and sweeps 

 until all the sand and smaller stones are swept to the edge 

 of the nest, leaving only the larger stones at the centre. 

 This removal of material from the certre cf the rest and its 

 accumulation at the border leaves the rest saucer-shaped. 

 At the centre the sand and fine gravel is removed, not merely 

 from the upper surface of the stones, but between them to a 

 considerable depth, so that the crevices between the stores 



