230 GENETICS 



chromosomes are the carriers of hereditary qualities 

 since extra chromosomes are always associated with 

 the character of sex. 



Second: The process of maturation, which always 

 results in halving the chromosome material of the 

 germ-cells as a preliminary step to fertilization, is a 

 series of complicated manoeuvers not practised by other 

 cells. During this process no other part of the cells 

 appears to play so consistent and important a role 

 as the chromosomes. Provided they act as hereditary 

 carriers, their peculiar behavior during maturation is 

 just what is needed to bring together an entire comple- 

 ment of hereditary determiners out of partial contri- 

 butions from two parental sources. 



Third: Sometimes abnormal fertilization occurs, as 

 in the case when two or more sperm-cells, instead of 

 one, enter the egg cytoplasm and unite with the egg 

 nucleus. This unusual performance has been artifi- 

 cially induced by chemical means in the case of sea- 

 urchins' eggs. The fertilized egg, or zygote, thus 

 formed with an excess of male chromosomes, results in 

 the development of abnormal larvae. It is thought that 

 a causal connection may exist, therefore, between the 

 additional male chromosomes in the fertilized ovum and 

 the abnormalities of the progeny. 



Fourth: The fact that chromosomes may retain 

 their individuality throughout the complicated phases 

 of mitosis, as has been proven in some instances, agrees 

 with the corresponding fact that certain characteristics 

 of the somatoplasm maintain their individuality from 

 generation to generation. 



Moreover, certain chromosomes in the fertilized egg 



