It would prove bewildering rather than instructive to go more deeply into the theoretical aspects of heredity and to discuss matters like the chromo some theory. There are, however, some points to be mentioned before focussing our attention upon man, Much confusion exists in this con: nection in the lay mind on account of general belief that acquired characters might be inherited. This is a very exceptional event or occurs 0 slowly that the process is only affeetive on a geological time-scale.
The complicated arrangement of chromosomes may in some respects be compared to that of the ancient Chinese pakua based upon the Yang-Yin principle, in which are cuimbinations of the lines, any one of which is supposed to Interpret some fundamental feature in philosophy, astrology, divination or medicine, Another point upon which misunderstanding exists concerns the relative merits of inbreeding and outcrossing, In numerous animal and plant species prolonged inbreeding may prove harmful, leading to the production of defective and sterile individuals, When on the contrary members of two different inbred lines are mated, there is usually a considerable' gain in vigour. Further research has shown, however, that inbreeding is not necessarily harmful. Most of its untoward effects, If any, appear within the first five to ten genera fons. By practising rigid selection during that period, a vigorous Inbreeding race maybe built up.
Two distinct views are held as to the advantage of outcrossing. "On the one hand it is assumed that the bad effects of inbreeding are merely ne to the appearance of recessive characters which it should be potsible to. eliminate by—selection. Other workers believe that heterozygoss Is beneficial as such. This Is certainly an involved question, As stated above, the first generation a cross between spacious is often larger and healthier than either parent. But the resulting" indivi-Guals may be sterile or yield in their turn very unsatisfactory offspring.
Text read from the printed page and cleaned; old type leaves the occasional error.