FERTILISATION 201 



reproduction of unicellular organisms ; in the former, however, 

 the metabolism of one cell, the spermatozoon, is by the process 

 of fertilisation combined with that of another cell, the ovum, 

 into a single resultant, the metabolism of the offspring that 

 arises from the fertilised ovum ; the offspring hence possesses 

 the characters of the two parents/' l 



In view of the considerations set forth above it must be 

 admitted that the question as to the respective parts played 

 by the nucleus and the cytoplasm in hereditary transmission 

 remains as yet unsolved. 



TELEGONY 



It used to be supposed that the spermatozoa of an animal 

 on being introduced into a female of the same kind, besides 

 fertilising the ripe ova and producing young, were capable of 

 exercising a permanent influence over the mother, and so trans- 

 mitting certain of their characters, not only to their own 

 immediate offspring, but to the future offspring of the mother 

 by another sire. This phenomenon, 2 in which many practical 

 breeders still believe, was called Telegony or Infection, and the 

 female was said to be " infected " by the previous sire. 



The classical example, and one in which Darwin 3 himself 

 believed, of the supposed influence of a previous sire upon the 

 future offspring, is the case of Lord Morton's quagga, which 

 was stated to have infected an Arab mare, so that she subse- 

 quently produced two striped colts by a black Arab horse. In 

 recent years Ewart 4 has repeated the experiment, employing a 



1 Verworn, loc. cit. Cf. Farmer (loc. c ?'.), who regards the chromo- 

 somes of the nucleus as representing primordia, which are responsible 

 for the appearance of the hereditary characters, but need to be supple- 

 mented by specific exciting substances which determine what particular 

 potential character shall actually develop. 



2 The phenomenon was explained by supposing that the young, while 

 still in utero, in some way affected the mother, and this influence was 

 further transmitted to the subsequent offspring. It will be seen that this 

 explanation assumes the possibility of the inheritance of acquired characters 

 of which there is little or no evidence. For recent reviews of this ques- 

 tion see Morgan, Experimental Zoology, New York, 1907 ; and Thomson, 

 Heredity, London, 1907. 



3 Darwin, The Variation of Animals and Plants under Domestication, 

 Popular Edition, vol. i., London, 1905. 



4 Ewart, The Penycuik Experiments, London, 1899. 



