DOUBTFUL PHENOMENA OF HEREDITY 385 



it would be possible to isolate the animals, and for the keepers 

 to exert a strict control over them for considerable periods of 

 time. 



The philosopher Carneri mentions a case which came under 

 his own notice. He kept a herd of cattle of the dark grey 

 Mlirzthal breed. On one occasion he put one of the cows to a 

 ' light-coloured Pinzgau ' bull instead of to one of the same 

 breed. The cow threw a calf with the characteristic brown and 

 white patches of the Pinzgau breed, as well as with distinct 

 traces of the ' dark grey Mlirzthal cross.' The cow was sub- 

 sequently covered by a Mlirzthal bull, and, contrary to expecta- 

 tion, the second calf was also a ' hybrid,' being for the most 

 part grey, ' but possessing large brown spots like those of the 

 Pinzgau breed.' 



Both the above mentioned cases are not so conclusive as they 

 appear to be at first sight. A drawing by Agasse of the foal 

 possessing the characters of the cjuagga is to be seen at the 

 Royal College of Surgeons in London, and shows indistinct 

 dark stripes on the neck, withers, and legs. Similar stripes are, 

 however, not very uncommon on purely bred foals, and ordinarily 

 disappear as the animal grows older. No further resemblance 

 to the quagga can. however, be detected in these pictures.* 



I must not omit to mention that before having heard of the 

 hypothesis of ' infection,' Carneri accounted for the case of the 

 two breeds of cattle described above by supposing that ' a drop 

 of Pinzgau blood' must have previously got into the Mlirzthal 

 herd without his being aware of it. 



Thus even the best of these 'cases' are not reliable and 

 actually convincing. We may, however, at any rate suppose 

 that this so-called ' infection,' if not altogether deceptive, only 

 occurs in rare instances, and by no means regularly, or at most 

 only in some cases. Experienced breeders, hke Settegast and 

 Kiihn of Halle, do not believe in it ; for although they have 

 frequently crossed various domestic animals, they have never 

 observed an instance of it. Such cases could only be accounted 

 for from our point of view by supposing that spermatozoa had 

 reached the ovary after the first sexual union had occurred, and 

 had penetrated into certain ova which were still immature. The 



* According to Settegast (' Thierzucht," Breslau, Bd. I., 1878, pp. 

 223-234). 



