74 NATURAL HISTORY OF AMIA OALVA LINNJ1US. 



Sometimes the male does not excavate a nest, but makes use of a natural depres- 

 sion of the bottom formed in suitable material, as shown by the following extract from 

 my note-book: "This nest does not appear to have been built at all. There is a 

 natural depression, the bottom of which is covered by the long slender dead leaves 

 of a shore sedge (?) or grass, leaves of the diameter of a knitting-needle. The little 

 sediment upon the surface of these leaves may have been fanned away. Upon the 

 leaves the eggs are laid, but the fish has apparently not removed any of them, but 

 has merely made use of the natural conditions." Similar instances are noted by 

 Fulleborn ('94), Whitman and Eycleshymer ('97), and Dean ('98). 



Small areas on the bottom are often found that are covered with fibrous rootlets 

 and devoid of growing plants, though walled in by such plants. These areas so closely 

 resemble nests as to be frequently mistaken for them. They may be told from 

 nests by the ooze that covers the rootlets in greater or less abundance; but this 

 ooze is often scant in such areas and they are then only to be certainly distin- 

 guished from nests by following their further history. These areas are to be found 

 wherever the shade is so deep and continuous that water plants do not grow well. 

 They are especially well marked under floating slabs of wood, floating stumps of small 

 masses of floating cattails which happen to be held in place by adjacent vegetation. 

 This vegetation largely excludes the side light and so deepens the shade and hinders 

 the growth of aquatic plants, but does not prevent the penetration of their rootlets 

 into the shaded spot. A strong wind or a freshet may remove the floating object and 

 leave the nest-like area fully exposed in free water. Such plantless areas are of 

 course the rule under logs, stumps, fallen trees, and bushes; and it is probably not 

 only the shelter afforded, but also the absence of growing plants that leads the fish 

 to select such places for hidden nests. Where the nests are built in the open, the 

 small size of the plant cuttings removed and their relative fewness shows that similar 

 plant-free areas are selected. The fish does not locate such nests on spots previously 

 thickly grown up with water plants and then tear out these plants, for in that case 

 considerable masses of such plants would mark the location of each nest. He selects 

 rather a relatively plantless area surrounded by a wall of growing plants, and from 

 this area removes the few young shoots and cleans up the rootlets. I have no 

 doubt that suitably prepared artificial nests placed on the spawning ground would 

 be utilized by the fish. If this account is correct, the nests are certainly not uni- 

 formly "in places to which the sun and warmth always have unhindered access" as 

 stated by Fulleborn ('94). 



G. Frequency. — The frequency of the nests depends largely upon the number of 

 male fish as related to the area of available spawning ground; though, owing to the 



