HYBRIDIZATION IN ANIMAL BREEDING 



519 



The male mule apparently never produces functional spermatozoa. 

 Wodsedalek has found that the horse and ass have different numbers of 

 chromosomes, so that the mule comes from the union of an egg-cell con- 



Fiu. 200. A mare mule (?) with a foal by a Percheron stallion. (After Lloyd-Jones.) 



FIG. 201. The foal of Fig. 200. It is said to exhibit mule-like characters in its feet 

 and actions, although otherwise its characters are all horse-like. (After Lloyd-Jones.) 



taining nineteen chromosomes with sperm cells containing either thirty- 

 two or thirty-three. In consequence reduction divisions in the mule 

 are prevailingly abnormal as to chromatin distribution, and no functional 

 spermatozoa appear to be produced. If we judge by analogy with plants, 



