THE CARRIERS OF THE HERITAGE 31 



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

 formed with an excess of male chromosomes, re- 

 sults in the development of abnormal larvae. It is 

 thought that a causal connection may exist, there- 

 fore, 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 have been identified with particular features in 

 the adult developing from that egg. Tennent sum- 

 marizes his recent work on Echinoderms (1912) 

 by the statement that from a knowledge of the 

 chromosomes in the parental germ-cells, particular 

 characters in the adult hybrids may be predicted, 

 and, conversely, that from the appearance of sexually 

 mature hybrids the character of certain chromosomes 

 in their germ-cells may be predicted. 



Again, the correlation of a particular chromosome 

 in the germ-cells with a definite adult character, 

 namely sex, has been repeatedly demonstrated in 

 connection with the so-called "extra chromosome" 

 to which reference has already been made. 



Fifth: Finally, excellent evidence of a definite 

 causal connection between certain chromosomes of 

 the germ-cells and particular somatic characters has 



