NATURAL HISTORY OF AMIA CALVA LINNAEUS. 105 



to hatch and for the larvse to leave the nest is necessarily dependent on the tem- 

 perature. Let the future critic then bear in mind that the materials under dis- 

 cussion are variable and that the behavior of the fish is plastic. 



2. Characteristic Features of the Breeding Behavior. — A casual acquaintance with 

 Amia leads at once to a comparison of its breeding habits with those of the 

 more familiar birds. A nest is found filled with eggs and guarded by the parent 

 fish. The nest is, therefore, the property of an individual pair of fish which have 

 prepared it together, and the fish which guards it is most likely the female. The 

 literature contains many such hasty generalizations concerning the breeding habits 

 of nest-building teleosts. Thus, to cite a few instances only, Estes (Hallock, '77) 

 refers to the parent which guards the young of Amia as "she." Agassiz ('57) 

 describes the male and female of Eupomotis gibbosus as keeping watch alternately 

 over the nest. Later Stone ('89) describes the female of the same species as the 

 nest-builder and care-taker. My own unpublished observations on Eupomotis 

 gibbosus have convinced me that, as surmised by Gill ('89), the female takes no 

 part in building the nest or guarding it. Again we find Arnold ('83) making the 

 statement that the female of Micropterus is the nest-builder, an error subsequently 

 rectified by Lydell (:02). In work of this sort the method used to distinguish the 

 sexes should always be stated. This is the more necessary since young males com- 

 monly resemble females. Where no suitable method is known to have been used, 

 the account must be rejected in so far as it concerns the participation of the sexes. 

 I have found in the literature no authentic record of a case in which the female, 

 unaccompanied by the male, prepares a nest in advance of spawning. In the 

 Salmonida^ the female makes an excavation in the bottom, but she does this in the 

 presence of the male, and the nest itself may be regarded as the result of the move- 

 ments of the female preparatory to spawning, rather than as a premeditated struc- 

 ture (see the excellent account in Brehm, '92). 



Darwin ('83) says of Crenilabrus massa and Crenilabrus melops that both 

 sexes work together in building the nest. Dr. H. M. Smith (:03) has recently shown 

 that in Ameiurus nebulosus, confined in an aquarium, both sexes take part in 

 building the nest, which is prepared in advance of spawning; and I have observed 

 two of these fish, probably male and female, working together at nest-building in 

 their natural habitat. In Ameiurus nebulosus in the aquarium, the care of the 

 young, although shared by both parents, falls more on the male than on the female, 

 while in Ameiurus albidus (Ryder, '83) the whole care of the young is assumed by 

 the male. I have several times observed the nests and swarms of the young of 

 Ameiurus nebulosus in their natural habitat, but have never found them guarded 



