NATURAL HISTORY OF AMIA CALVA LINN.EUS. 77 



Table IV shows when the eggs were laid in the thirty-one nests. 



TABLE IV. 



Observed to be laid by day 4 



Nest found empty and later on the same day with eggs in early cleavage 2 



Found at 1 P.M. in 2- to 4-cell stage, estimated to have been laid between 9 and 10 A.M 1 



Found at 10 P.M. in late cleavage, laid at 12 M 1 



Total laid by day 8 



Found in late cleavage 4.30 P.M., estimated to have been laid 6.30 A.M 1 



Found in 2- to 16-cell stage at 5 to 7 A.M., estimated to have been laid between 2 and 4 A.M 8 



Found in late cleavage 8 A.M. to 12 M., estimated to have been laid between 10 P.M. and 2 A.M.. . . 14 



Total laid at night 23 



The rate of development depends upon temperature. In the tables given by 

 Dean ('96), and by Whitman and Eycleshymer ('97), the temperature is not given, 

 and in collecting cleavage stages I did not note it at the time. Nevertheless, in all 

 these cases the eggs were undoubtedly laid at the usual temperature at which Amia 

 spawns, i.e., not far from 18 C., and the temperature during the few hours following 

 the spawning is not likely to have changed sufficiently to have greatly modified 

 the rate of development of the eggs. The only doubtful case seems to be that of 

 the eggs estimated to have been laid at 6.30 A.M. These may have been laid before 

 daylight or after. In general, we may say that spawning takes place two and one- 

 half to three times as often by night as by day. In the four cases where spawn- 

 ing was actually observed it occurred between 3 and 4 P.M., 5 and 6 P.M., 10 and 

 12 A.M., and at 3 P.M. Whitman and Eycleshymer ('97) noted one case of spawn- 

 ing by day and quote Ayers as having observed "some cases in which the eggs were 

 cast in the afternoon." Ayers is further quoted as saying that "The nest-forming 

 process generally begins at early dawn, and the eggs are cast about sunrise." 



That the sexes are able to detect one another at considerable distances, and that 

 the females seek the nests prepared by the males, is indicated by the following obser- 

 vations: An empty nest, not yet finished, was found on June 1. On June 3 it 

 appeared to be completed and was occupied by the male. "I then saw the female 

 at a distance of about 12 metres from the nest and with her head pointed toward 

 it. She became frightened and disappeared into deep water." Further evidence 

 of the power of one sex to detect the presence of the other is afforded by the presence 

 of strange males about nests in which spawning is going on and by the following 

 experience: In 1900 twenty-one females were confined in a crate of slats, spaced 

 about 2.5 centimetres apart, so that water could enter between them. The crate 

 was nailed to stakes so that its bottom was about 30 centimetres from the bottom 

 of the pond. At six o'clock on the morning of April 26 a large number of males, 



