REPRODUCTIVE CYCLE. 109 



is to be found in the preceding sexual activities. Fertilization is not necessary, 

 as a pair of females may stimulate each other. When a female is stimulated by 

 another female acting as a male there is a more frequent lack of eggs than in normal 

 conditions. This deficiency may be due either to the lack of sperm or sperm 

 effects or to the inadequate masculine behavior of the mate. Feminine modes 

 of behavior constitute a favorable though not an essential condition, for the female 

 which assumes the masculine role does not lay as frequently as her mate; more- 

 over, in those cases in which she does lay, her eggs are often several days late. 

 Contact is efficacious, but not essential. As Fulton says, "neither contact nor any 

 of the activities of a mate are essential; a young and rank bird will occasionally 

 lay without a mate." Undoubtedly ovulation may occur in a female that occupies 

 a cage alone. These cases were almost certainly preceded by a rise of the sexual 

 impulse. Probably ovulation is normally a result of all the preceding conditions, 

 the sexual impulse, its various modes of expression, and the stimulus resulting 

 from the behavior of the mate. The relative efficiency of these factors may be 

 variable, and at times a deficiency in any one may prevent ovulation, while in 

 other cases ovulation may occur when but one condition is present. 



MISCELLANEOUS. 



The motive to any act is an ingrained impulse or disposition toward some 

 sensory stimulus. The bird acts as it does because it "feels" disposed to do so; 

 it acts in harmony with its feelings and impulses of the moment. The act brings 

 certain sensory results which are satisfying, and these results may enter into the 

 motive subsequently. The acts also achieve other results with a biological utility; 

 but these advantages may constitute no part of the actuating motive and bring 

 no satisfaction to the bird. To the bird these results are mere incidental by- 

 products, without meaning or significance. Many proofs of this conception are 

 offered. Such activities as seeking a nesting-site in a new locality, construction 

 of a nest, and roosting away from the nest at night are manifested under environ- 

 mental conditions in which they are entirely gratuitous and unnecessary. Birds 

 will incubate without eggs or young; or they may desert either eggs or young. 

 In satisfying their impulse to remove the shells, the parents have been known to 

 deposit the fledglings on the floor of the cage and leave them to perish and the 

 young may be injured or killed in the act of feeding. 



While the organization of the cycle of activities has been perfected, probably 

 by natural selection, to achieve certain results, the adaptation need not be absolute 

 and letter-perfect. The theory of natural selection demands only a practical 

 perfection sufficient to secure the survival of the species in their conditions of 

 life. Not every egg need be hatched nor every young be reared. Moreover, the 

 utility refers only to those conditions in which the organization was developed. 

 On this basis certain acts, which appear unutterably stupid and non-intelligent 

 from the human point of view, are rendered more comprehensible. Although 

 the young birds may be cast from the nest along with the shells, or seriously 

 injured in the process of feeding, or eggs and young be heartlessly deserted, or the 



