NATURAL HISTORY OF AMIA CALVA LINNiEUS. 



67 



made. The nests were nearly all without eggs when found, and in the few cases 

 in which they contained eggs these were in early stages from which the date of 

 building the nests could be approximately determined. 



The table shows the optimum temperature for nest-building as accurately as 

 could be expected under the conditions which obtain. The large numbers in the 

 upper row under 14 and in the lower row under 13 may have been the result 

 of a sudden unrecorded change of temperature. That there is no constant relation 

 observable between nest-building in Amia and plant growth is due to the fact that 

 the optimum water temperature for Amia may occur for several days at any stage 

 in the early spring growth of aquatic plants and may thus bring on the nest-building 

 either while the aquatic plants are still small or after they have reached a consid- 

 erable growth attained at a temperature below the Amia optimum. The relation 

 of this optimum temperature for Amia to the activities of other aquatic vertebrates 

 is not so clear, but is probably of similar sort. 



B. Localities. — The localities selected for nests are quiet bays or inlets well 

 grown with water plants and affording shelter for the nests in the form of stumps, 

 bushes, or fallen trees. Those localities are preferred in which the removal of the 

 growing vegetation leaves a thick mat of fibrous rootlets for the bottom of the 

 nest. One such bay of the Huron River, running back from the Lowell mill-pond, 

 was about two hundred metres long and had a width of thirty metres near its 

 junction with the pond. For three years it contained each year twenty-four or 

 twenty-five nests. In another locality the nests were built one year among the 

 grass-tufted hummocks (called "tetes de femmes" by the French fishermen) of a 

 submerged meadow. In order to reach them the fish must follow the tortuous 

 passages between the hummocks, but the rootlets of the meadow grass made ideal 

 nest bottoms. 



C. Nests. — Each nest is a saucer-like excavation from 30 to 90 centimetres 



