REPRODUCTION l6l 



beast. Undeniably, when properly regarded and controlled, it constitutes 

 the mainspring of action in many of the most vital, romantic and sacred 

 relations of human kind. Yet it is only part of life in this universe of so 

 many interesting things and' experiences, and therefore is something that 

 should be kept in its proper place. Those modern advocates of "being 

 natural" or "getting back to nature" as they vociferously proclaim their 

 doctrine, may well note that through the whole realm of animal life, from 

 the lowliest to the liighest almost without exception, actual sex function 

 is paramount during only a brief period of the animal's career and there- 

 fore plays but a secondary role in its total existence. 



Without sex the world of plant and animal life would certainly seem 

 very strange. There would be no flowers. In the animal world there would 

 be little difference in appearance among the individuals of a species since 

 there would be no necessity for discriminating male from female. Orna- 

 mentation and the displays of courtship often incident to mating would 

 be nil. The power of making sounds, even, might not have developed 

 since it is most commonly used as an aid to mating. The songs of birds, 

 the stridulations of such insects as katydids, crickets or cicadas, the spring 

 trilling of creatures like male frogs, the various calls of different mammals 

 have probably all arisen primarily as sex calls which insure the bringing 

 together of male and female at mating time, even though later such sounds 

 have often taken on other functions. The bellowing of bulls or the cater- 

 wauling of tomcats are vocal challenges more indirectly associated with 

 mating, while the familiar clucking and warning signals of hens and various 

 other female forms is an extension to the protection of young. Vocaliza- 

 tions of various kinds often come eventually to serve for the welfare of 

 flocks, herds, or other social groups. And in man, of course, voice has ad- 

 vanced into articulate speech and all the advantages associated with lan- 

 guage. 



Sex is determined ordinarily by a chromosomal mechanism in the germ 

 cells. In man, for example, with his 48 chromosomes (24 pairs; one of each 

 kind from each parent) there is a special pair of chromosomes, called the 

 XY pair, which, unlike the others, do not match. The Y member of this 

 pair is smaller than the X member. In one of the last divisions of the matur- 

 ing germ cells the various corresponding pairs of chromosomes line up 

 side by side {synapsis) in such a way that in the ensuing cell division each 

 of the two newly formed cells receives one or the other member of a pair 

 but not both. Thus X would go into one of the new cells. Y into the op- 

 posite one. In this way each definitive germ cell while receiving only 

 half (24 in man) of the original number of chromosomes, gets one of 

 each pair; that is, one of each kind. This is called the reduction division. The 

 original number (48 in man) is restored at the time of fertilization: 24 

 being contributed by the spermatozoon and 24 by the ovum. Whether 

 a given chromosome of the reduced set is of maternal or paternal origin 



