82 NATURAL HISTORY OF AMIA CALVA LINN.EUS. 



ripe. The abdomen did not become softer, and at no time was it possible to strip 

 them. Finally, three of those that seemed softest were opened, but no eggs were 

 found in the oviducts or body cavity, nor could the eggs be removed from the 

 ovaries without injury. Attempts at artificial fertilization of these eggs failed. 

 Nevertheless a few eggs were laid in the crate and were found adhering to its 

 bottom and sides. 



Male and female fish were also placed together in a square enclosure of netting 

 about 5 metres on each side and on the natural spawning ground. Three males in 

 brilliant breeding colors and two apparently ripe females were used. The experi- 

 ments continued for eleven days, but no nests were made and nothing of importance 

 noted, except that a few eggs were laid along the netting and adjacent vegetation. 



The usual course of nest-building and spawning may here be briefly summa- 

 rized as follows: In water of 30 to 60 centimetres depth with abundant growing 

 plants, males select small areas on the bottom which are relatively free of growing 

 plants and are often concealed, and from these by movements of the body and 

 fins and perhaps by biting they remove the few plants and the bottom ooze so as 

 to leave exposed the fibrous roots of the plants or the sand, gravel, or other sub- 

 jacent material. The nests are thus excavated in the absence of the females, and 

 chiefly at night. Their proximity to one another varies with the number of males 

 as related to the area of available spawning ground and with the character of the 

 ground. These nests, while still empty, are guarded by the males for usually 

 twenty-four to thirty-six hours, but often for a much longer time. They are then 

 usually approached by the females and the spawning takes place. If the female 

 does not appear, the nest is abandoned. The spawning is intermittent, and the 

 characteristic spawning movements last from one to three hours, during which the 

 fish are very active. During the spawning movements there is no evidence that 

 the male displays his colors before the female. Sexual excitation of the female is 

 produced rather by biting and stroking. In some cases a single female probably 

 spawns in more than one nest. A single male may, after an interval of some days, 

 receive a second female into his nest, and her eggs may be laid along with those 

 previously in the nest or may supplant them. The number of eggs laid in a nest 

 varies greatly. I have seen as few as 25 freshly laid. The maximum number is 

 probably many thousand, but I have never counted them. They may be over the 

 whole inner surface of the nest, on the bottom only, or on one side only, If fibrous 

 roots are present they are invariably on these. 



6. Guarding the Eggs; Protective Colors of Male — While guarding the nest both 

 before and after it is filled with eggs the male lies at times directly on the nest, 



