158 HEREDITY AND SELECTION IN SOCIOLOGY 



eliminating former id complexes. And yet the embryonic 

 development of the human being clearly illustrates the 

 obstinacy with which the plasms of the Amoeba and of our other 

 ancestors have persisted throughout the immeasurable periods 

 of time which have elapsed. Haeckel has distinguished no fewer 

 than fourteen difierent stages ia the early embryogenesis of 

 man, which recapitulate the abbreviated history of fourteen 

 different ancestors — Protozoa, Gastrooea, Protochordate, etc. In 

 the chapter on the Lamarckian Hypothesis we saw that this 

 very remarkable phenomenon is to be explained by the fact 

 that a minority of old deternoinants, representing a former 

 organic condition, may still remain ia the germ-plasm in spite 

 of transformations in the constitution of the organism, and may 

 persist throughout long periods of time ; though its influence on 

 the ontogeny becomes gradually less and less until there is com- 

 plete disappearance, or until the disappearance is, at any rate, 

 so far complete that it manifests itself only in the earhest stages. 

 In a previous chapter we noticed the so-caUed " reducing 

 division " which is effected in the germ-cells before maturation. 

 This division differs from the ordinary ceU division, since, in 

 the latter, the chromosomes divide into two equal groups, 

 forming the equatorial plane of the karyokinetic figure, and 

 then proceed to move apart and to approach the poles ; whereas 

 in the former there is no previous halving of the chromosomes, 

 but these are at once divided into two equal parts, one of which 

 is bequeathed to each of the daughter nuclei. Two such 

 divisions follow close on one another, and the result is the 

 reduction of the original number of chromosomes in the egg 

 by one-half.i The second maturation division is usually the 

 " reducing division," by which the chromosomes are reduced 

 to one-half their original number. 



1 The original number of chromosomes has previously been doubled, 

 and this obviates the reduction of the number to one-fourth as a result of 

 the two successive divisions. 



