144 TELEGONY AND REVERSION. 



feeble that, instead of leading to a reversion towards the 

 hypothetical "mid-parent" of the remote ancestry— that 

 is, to oif spring combining to a limited extent tlie characters 

 of the ancestors of both the horses and the zebras,— it may 

 only set up sufBcient disturbance in the reproductive sys- 

 tem of the dam to lead to a slight regression towards her 

 own particular and not very remote ancestors. 



Before describing Mulatto's second foal, the cjuestion 

 may be asked, what amount of striping or other changes 

 would be required to conclusively prove she has been 

 "infected" by the zebra? Obviously if the germ-plasm 

 of the first sire unites with a maturing egg, the previous 

 sire could only enter into the formation of the second foal 

 to a vei'y limited extent. According to Mr. Galton's law 

 of ancestral heredity, the two parents contribute one half, 

 the four grandparents one fourth, the eight great-grand- 

 parents one eighth, and so on, to the total heritage of the 

 average offspring. If this law holds it follows that the 

 male jjarent only contributes one fourth of the total heri- 

 tao'e. If the previous sire contributed equally with the 

 reputed sire, the proportion would be one eighth for 

 each. But eveu if we admit that an immature egg may 

 contain the whole of the male germ-cell of a previous sire, 

 i. e. one eighth, this would be halved during the " re- 

 ducing division" of the nucleus; hence, at the most, the 

 contribution of the previous sire would be one sixteenth, 

 but actually (supposing there is direct " infection " of 

 the ovum) in the vast majority of cases considerablj^ less. 

 Further, the half not contributed by the parents would 

 be mainly provided by the ancestors of the dam. Hence, 

 when the most liberal allowance is made, the previous sire 

 could only under ordinary circumstances enter to a very 

 limited extent into the subsequent offspring. It is true 

 that the colt and filly bred by Sir Gore Ousele}' from Lord 

 Morton's mare were more richly striped than the quagga 

 hybrid. This has ahvays seemed to me to prove that the 

 majority of the stripes in the Gore Ouseley " colts " were 

 inherited directlv from the black Arabian. 



