THE CARRIERS OF THE HERITAGE 



have been identified with particular features in the 

 adult developing from that egg. Tennent summarizes 

 his 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 refer- 

 ence 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 been fur- 

 nished by certain critical experiments upon the eggs 

 of sea-urchins. Boveri found that he was able in some 

 instances to shake out the nuclei bodily, chromosomes 

 and all, from the mature eggs of the sea-urchin, 

 Splicer echinus, and when there was added in sea water to 

 such enucleated eggs the sperm-cells of an entirely 

 different genus of sea-urchin, namely, Echwws, the 

 Echinus sperm-cells entered the Sphcerechmus eggs, 

 which had been robbed of their nuclei, and from this 

 peculiar combination larvae developed which exhibited 

 only Echinus characters! 



Such cumulative circumstantial evidence as the fore- 

 going has convinced many that in the chromosomes we 

 have visibly before us the carriers of heredity. 



In any event the supposition that the chromosomes, 



