5iS LIFE : OUTLINES OF GENERAL BIOLOGY 



synchronises with toying with building materials ; and changes in 

 the two activities occur simultaneously and are proportionate in 

 intensity. (4) The fourth phase concerns incubation and the care 

 of the young. The female loses susceptibiHty to sex-stimulation and 

 this reacts discouragingly on her mate. It is difficult to tell what 

 evokes the female's brooding, and the difficulty is not lessened by 

 the fact that she will sometimes brood on an empty nest. What can 

 be said save that brooding is a primary response, rhythmically 

 induced, part of the hereditary pattern, instinctive as many would 

 say, though Howard declines to use the word. When the young are 

 hatched, their note of hunger is a powerful stimulus to the mother, 

 and yet when she brings food to the gaping youngsters, she may 

 swallow it herself! 



Soon after the young birds leave the nest the sex-cycle may begin 

 again, but it is a remarkable fact that the influence of the offspring 

 remains upon the male more than upon the female. There appears 

 to be some "secondary physiological control" (requiring further 

 analysis) which operates in the female, but not in the male. Thus, 

 when the new cycle begins, she is finished with the young, and 

 ignores their appeal. In the buntings, they would be lost if it were 

 not for the still persistent paternal care. Similarly, at a different 

 period in the cycle, the male Whitethroat builds before he has been 

 found by a hen ; and the male Lesser Whitethroat not only builds, 

 but sits upon the nest. The male is ahead of the female in suscepti- 

 bility to both sexual and parental stimulation. 



It seems to be an outstanding fact that the inherited pattern of 

 reactions has unity or combined singleness. The bird is an integrated 

 whole and it behaves as such. How is this unification brought about? 

 An important factor is that any one reaction wanes in the course 

 of prolonged excitation, not by muscular exhaustion or the like, 

 but in some subtler way like "fatigue" in a reflex. This waning 

 lessens the risk of overdoing any one line of activity, say fighting, 

 and tends to effect a harmony of reactions, which makes for the 

 attainment of a common biological end, namely, the production of 

 a brood at an appropriate time. The waning of the reaction leaves 

 the "common path" free for a different reaction, and conflict of 

 reactions is thus avoided or lessened. The waning of a reaction under 

 prolonged excitation is an automatic integrative agency. 



Howard has gone further than his precursors in working out a 

 connected story of the successive events in the reproductive 

 behaviour, and in showing how they are co-ordinated towards the 

 end-effect— namely the effective production of a brood. We cannot 

 do more than mention a few instances of this ; the fixing on a territory 

 helps towards the subseciuen't feeding of the young; the conspicuous- 

 ness of the perch and the vigour of the song attract the visit of a 

 female; her presence stimulates the male and she enjoys the com- 



