76 NATURAL HISTORY OF AMIA CALVA LINNAEUS. 



at 11 a.m. it contained eggs in cleavage stages and therefore laid on the night of 

 April 25. The eggs were very few in number. The male was still guarding the 

 nest, and it contained eggs on April 28 at 9 a.m. ; but on April 29 at 9 a.m. the eggs 

 had disappeared. The male was guarding the empty nest at 7.30 a.m. on April 30. 

 This is a period of five days, during three of which the nest contained eggs, but 

 whether in this case the original male had cleaned his nest of its unsatisfactorily 

 few eggs and was awaiting a second female, or whether he had been displaced by 

 a rival male, is uncertain, though the first supposition is by far the more 

 probable. 



The periods given above are those observed and are in nearly every case con- 

 siderably shorter than the actual periods; for it is always likely that the nest 

 was guarded for some time before any observation was made on it, and that 

 when, in later visits, it was found empty the male was often only temporarily 

 absent. 



If the female does not appear, the waiting male ceases after a time to guard 

 the empty nest. The nest then becomes gradually obliterated by the deposit of 

 sediment and plant debris, and in some cases by the ingrowth of the adjacent aquatic 

 plants. In most cases the nest returns more or less to the condition of the nest-like 

 areas already described. 



5. Spawning — I have been able to determine the time of day at which Amia 

 spawns in thirty-one cases. In four of these the actual spawning was observed. 

 In two the nests were found empty, and a few hours later they were full of eggs in 

 cleavage stages. In the remaining cases the nests contained eggs in cleavage stages 

 when found, and the time when they were laid has been reckoned by the use of the 

 table given by Whitman and Eycleshymer ('97, p. 321). This table shows that the 

 eight-cell stage is reached about four hours after deposition of the eggs, and the 

 late cleavage ten hours after deposition. By late cleavage I understand a stage 

 in which the upper small cells are just visible with a hand-lens (Whitman and 

 Eycleshymer, '97, p. 339, Fig. 10). The stage of these, as of other eggs, was deter- 

 mined at the time of finding the eggs, by fixing a few in formol-bichromate J acetic 

 acid,* transferring to water after 10 or 15 minutes, removing the shell with needles 

 and examining with a dissecting microscope. 



* A solution is made containing 2.5% of potassium bichromate and 10% glacial acetic acid. To this at the 

 time of use is added commercial formol (40% formaldehyde solution) in the ratio of one part of formol to twenty 

 of the- solution. In preserving eggs for embryological use the fluid is allowed to act for 8 to 12 hours, then replaced 

 with 4% formol, which is changed until it remains clear. The eggs are preserved in the formol. With this 

 fluid the eggs are not distorted by shrinkage of the shell, the histological details are well preserved, and the yolk cuts 

 more readily than with any other fluid that I have used. 



