X] 



Heredity and Sex 



169 



Admittedly there are difficulties in the way of this method 

 of representation but they seem to be no greater than those 

 besetting the hypothesis that maleness is dominant"^. 



Correns (81, 72, 75) has observed another group of facts, 

 doubtless important though equally difficult of interpretation, 

 in regard to the results of breeding from species which 

 have female, and hermaphrodite or gyno-monoecious indi- 

 viduals. His experience is that when the females are used 

 as mothers and are fertilised with pollen from the her- 

 maphrodites, the offspring are almost exclusively female. 

 When however the hermaphrodites are used as mothers 

 the offspring are mostly, though not so exclusively, her- 

 maphrodites. From experiments of this kind it is likely 

 that a good deal of light will be obtained when statistics 

 on an ample scale are available. Those who may under- 

 take such work will of course remember that as the consti- 

 tution of the individuals may be dissimilar, each must be 

 separately tested. 



The relation of dioecious to hermaphrodite and monoe- 

 cious forms will not in all probability be satisfactorily or 

 rapidly elucidated until some case can be found in which 

 the two types can be crossed together with a fertile result. 

 No evidence from such a case as that of Bryonia is free 

 from the suspicion that the sterility of F^ may itself be 

 introducing a complexity. 



Heredity limited by Sex: the Horns of Sheep. 



I now pass to the consideration of evidence as to 

 the part which sex plays in determining or limiting the 

 descent of certain characters in heredity. The manner in 

 which these effects are shown is well illustrated by the 

 following example investigated by Professor T. B. Wood 

 (312, 313) in the case of horned and hornless sheepf. As 

 a horned breed he chose the Dorset Horned, in which the 



* A fragment of evidence bearing on these problems is that contributed 

 by Gartner's experiment with Lychnis diurna ? crossed with pollen from 

 Z. flos-cuculi ^ . This gave 4 males and 2 females ; but of these, one 

 only, a female which was totally sterile, gave any certain indication of 

 having resulted from the cross. Pending a repetition of the experiment no 

 conclusion can be drawn with much confidence from this account. 



t As was stated before, hornlessness is a dominant in both sexes so far 



