86 NATURAL HISTORY OF AMIA CALVA LINNAEUS. 



mals and birds the males of Amia were doubtless, while on the spawning grounds, 

 much subjected to their attacks, and their coloration must then have been of some 

 use. That the colors themselves were produced in adaptation to these conditions 

 may be doubted, but that the color pattern is such an adaptation and may have 

 arisen through selection is hardly doubtful. 



7. History of the Eggs and Young Larvae in the Nests. — The eggs have been 

 accurately described by Whitman and Eycleshymer ('97). In the eggs found near 

 Ann Arbor the calotte is white and the yolk is of a very light yellow, nearly white. 

 The eggs, seen in mass, are therefore very conspicuous in their earlier stages. I 

 have never seen eggs of the brown color figured by Whitman and Eycleshymer ('97). 

 In the nest the eggs hatch in from eight to ten days at the usual temperature, 

 though as noted by Dean ('96) and Fiilleborn ('94) this period may be either pro- 

 longed or shortened by temperature. When hatched the larvae are about 7 milli- 

 metres long, colorless and incapable of progressive movement, and they either 

 attach themselves to the nest material by the adhesive organ at the end of the snout 

 and remain suspended in a vertical position or lie on their sides on the bottom. 

 They remain in the nest for about nine days after hatching. In one case noted the 

 eggs hatched on the ninth day and the larvae were found leaving the nest on the six- 

 teenth day. In a second case the eggs hatched on the ninth day and the larvae left 

 the nest on the eighteenth day. While the larvae are still in the nest the following 

 changes, repeatedly observed in fish taken from the nest from day to day, may be seen : 



A. Increase in length to about 12 millimetres (see Whitman and Eycleshymer, 

 '97, and Fiilleborn, '94). Measurement from five broods about to leave the nest 

 showed 11, 11.5, 11.5, 12, 13 millimetres. Those which measured li millimetres had 

 left the nest next day. 



B. Changes in the size and form of the yolk-sac. At 9 millimetres it is egg- 

 shaped as observed by Whitman and Eycleshymer, with the smaller end directed 

 backward. At 11.5 millimetres it is elongated, flat and irregular, about 2.5 by 1 

 millimetre, and lies on the right side of the larva. 



C. The pectoral fins become vertical, as noted by Whitman and Eycleshymer. 

 There are as yet no pel vies. 



D. Black pigment develops gradually until at 12 millimetres the whole body 

 is very dark greenish black or greenish brown, except the ventral surface, which is 

 dirty white. The iris is metallic golden. 



E. The use of the adhesive organ becomes gradually less, so that by the time 

 the larvae have reached a length of 12 millimetres it is no longer functional and the 

 larvae swim continuously. 



