of Philip, a text among those found at Nag Hammadi: Whomever the woman loves, to him those who are born are like; if her husband, they are like her husband; if an adulterer, they are like the adulterer. Often when a woman sleeps with her husband, but while her heart is with the adulterer with whom she is accustomed to unite, she bears the one whom she bears so that he is like the adulterer. The concept of telegony was revived with the rediscovery of Aristotle in the Middle Ages. This was part of the resistance to the marriage in 1361 of Edward, the Black Prince, heir to the throne of Edward III of England, with Joan, the Fair Maid of Kent, who had been previously married: their progeny, it was thought, might not be completely of his Plantagenet blood. Understandings in the 19th century and the collapse of the theory in the 20th In the 19th century, the most widely credited example was that of Lord Morton's mare, reported by the distinguished surgeon Sir Everard Home, and cited by Charles Darwin. Lord Morton bred a white mare with a wild quagga stallion, and when he later bred the same mare with a white stallion, the offspring strangely had stripes in the legs, like the quagga. The Surgeon-General of New York, the physiologist Austin Flint, in his Text-Book of Human Physiology (fourth edition, 1888) described the phenomenon as follows: Both Schopenhauer and Herbert Spencer found telegony to be a credible theory; August Weismann, on the other hand, had expressed doubts about the theory earlier and it fell out of scientific favor in the 1890s. A series of experiments by James Cossar Ewart in Scotland and other researchers in Germany and Brazil failed to find any evidence of the phenomenon. Also, the statistician Karl Pearson tried to find an evidence for telegony in humans using family measurement data and the statistical methods he invented, but failed to conclude that the steady telegonic influence really exists. Biologists now explain the phenomenon of Lord Morton's mare with reference to the dominant and recessive variants of a gene: both the mare and the stallion had a recessive gene; the foal inherited these alleles and thus displayed the characteristic invisible in its parents. In mammals, each sperm has the haploid set of chromosomes and each egg has another haploid set. During the process of fertilization