68 NATURAL HISTORY OF AMIA CALVA LINNAEUS. 



in diameter and from 10 to 20 centimetres deep. The bottom of the excavation 

 is usually of the fibrous roots of water plants, which, freed of all earth, form a thick 

 spongy mass. Sometimes, however, the bottom is of gravel or sand or even of 

 black loam, and in two cases it has been of the dead, brown, water-soaked stems 

 or leaves of cattail or other similar water plants. In one case a stone 20 centi- 

 metres in diameter was found on a nest bottom. The sides of the nests are usually 

 of rootlets and of growing plants, though occasionally they are of gravel. The 

 figure by Dean ('96) represents very well many of the nests that I have seen, though 

 the nests vary considerably in different localities. I have never seen a nest in which 

 "the soft weeds and rootlets appear bent and brushed aside in a way that gives it 

 somewhat the appearance of a crudely finished bird's nest" as described by Dean ('96). 

 D. Nests Built by Males. — That the nests are not made by the circling 

 of the two fish while spawning or before spawning (Dean, '96; Ayers as quoted by 

 Whitman and Eycleshymer, '97), but are built by the male in advance of spawning, 

 as surmised by Fiilleborn ('94), and without assistance from the female, and are 

 then, while still empty, guarded by the male, seems to me to be shown by the follow-* 

 ing observations: 



1. Of the one hundred and seventy-seven nests of which records have been 

 kept, eighty-one had not been spawned in when first observed. Forty-seven of 

 these empty nests were observed to be guarded by the male fish. Each of the 

 nests was revisited from day to day so long as it showed anything of interest, and 

 at many of these successive visits the male fish was found guarding the empty 

 nest. This was the case seventy-four times with the forty-seven nests and three 

 times with many of the individual nests. At none of these visits was any female found 

 on or near a nest until the spawning took place. That the male was not seen on 

 all the eighty-one empty nests and was not found at every visit made to the forty- 

 seven nests observed to be guarded is due to the fact that he is frequently absent 

 from the nest. Thus a nest unguarded at one visit is often found guarded at one 

 or more later visits. 



2. Of these forty-seven nests six were not yet completed when discovered, and 

 were later found to be completed. In a number of these cases the male was seen 

 at work excavating the nest, as noted in another place (see nest-building). No 

 female was ever seen near such a nest. 



3. In the seasons of 1898 and 1900 an attempt was made to get experimental 

 evidence of the part played by the sexes in making the nests. The entrance to 

 one of the little bays extending back from the Lowell mill-pond was closed by a 

 fyke net. The bay selected was one in which there had been about twenty-four nests 



