79 6 



EMBRYOLOGY 



twins, February 4, 1867, in New Kent County, Virginia. One of these 

 twins was black, the other was white. Frances is a mulatto. The black 

 child is much darker than she is. Previous to the parturition, she had 

 given birth to seven children, all single births. She was living at the 

 time of her impregnation in the family of a white man as house-servant, 

 sleeping with a black man at night. She insists, however, that she never 

 had carnal intercourse with a white man. She probably does this because 



Fig. 219. Formation of the blastodermic vesicle (van Beneden). 



A, B, C, D, sections of ova in successive stages of development in the rabbit ; zp, zona pellucida ; 

 <?/, epiblastic cells ; hyp, hypoblastic cells. 



the black man turned her out of his house when he saw that one of the 

 children was white. The only negro feature in the white child was its 

 nose. There, its resemblance to its mother was perfect. Its hair was 

 long, light, and silky. Complexion brilliant:" 



It is a curious fact that when a cow produces twins, one male and 

 the other female, the female, which is called a free-martin, is sterile and 

 presents an imperfect development of the internal organs of generation. 

 This has led to the idea that possibly the same law may apply to the 

 human subject, in cases of twins, one male and the other female; but 



