OTHER METHODS OF SEX-DETERMINATION 239 



explanation, since Whiting has shown that some of these 

 exceptional black males may breed as though all their 

 sperm carried only the orange gene of the mother. But 

 there are other facts indicating that in these cases the 

 explanation is not so simple as this, for most of the black 

 males are sterile, as well as the few daughters arising 

 from those males that are fertile (the mosaic males ).^ 

 Whatever the final solution may be for these exceptional 

 cases, the main results of the crosses confirm the theory 

 that the males are haploid. 



Sex in Haploids. 



The demonstration by Allen in 1919, that the cells of 

 the female haploid gametophyte of the liverwort, Sphae- 

 rocarpus, have a large X-chromosome and that the cells 

 of the male haploid gametophyte have a corresponding 

 small Y-chromosome, gives a reasonable explanation of 

 the differences shown by their prothallia (gametophytes). 

 Similarly the experimental demonstration by the Mar- 

 chals, by Wettstein and others that from each spore- 

 mother-cell of dioecious mosses two spores arise that de- 

 velop into female protonemata (gametophytes), and two 

 other spores that develop into male protonemata (game- 

 tophytes), falls into line with Allen's results on the allied 

 liverworts. It is customary to speak of the two kinds of 

 gametophytes as female and male respectively since one 

 produces eggs the other sperm cells (antherozoids). The 



5 According to Anna E. Whiting (1925), "the black-eyed patroclinous 

 males show a higher percentage of morphological abnormalities than do 

 males and females normally produced. The majority of patroclinous males 

 tested have been sterile, some have bred as blacks and been partially fertile, 

 while a few mosaics have produced orange-eyed daughters and have been 

 fully fertile. The orange-eyed daughters of patroclinous males are normal 

 in morphology and fertility. The black-eyed daughters of patroclinous males 

 are few in number and show a large percentage of abnormalities and are 

 almost completely sterile." The exceptional males in Hadrobracon may ex- 

 plain some of the anomalous cases that have been recorded in honey bees. 



