THE CYCLE OF SEX 117 



CHAPTER VI 



THE CYCLE OF SEX 



The curve of life Childhood Adolescence in general 

 Puberty in man Courtship among animals Falling 

 in love Married life and parental affection The 

 difficult age and senescence. 



THE CURVE OF LFFE. The course of an 

 individual life may he conveniently repre- 

 sented by an ascending and descending curve. 

 There is the ascent of development and 

 growth ; there is the period of maturity, 

 full strength and reproduction; and there 

 is the descent of waning powers and senes- 

 cence. In adaptation to particular conditions 

 of life and as expressions of particular consti- 

 tutions, there is among animal types a 

 remarkable diversity in the shape of the 

 curve. There are great differences in the 

 relative proportions of the successive chapters 

 in life. There may be slow or rapid embryonic 

 development witness the contrast between 

 the salmon with its years of growth and the 

 blow-fly complete in a few days. There may 

 be a long larva! period, as in the frog, or none, 

 as in the snake; there may be a prolonged 

 adolescence, as in an eel, or a precocious 

 maturity as in a rat. Here we see a lengthen- 

 ing out, and there a not less remarkable 

 telescoping. What a contrast, for instance, 

 between may-flies with a long aquatic larval 

 life of two or three years and a short aerial 

 adult life of two or three days, and the 

 majority of, say, amphibians with their 



