42 



THE CHROMOSOMES 



Male plant 6 pairs of autosomes, X, Y^, Y^ 

 Female plant 6 ,, ,, X, X. 



In this case it will be seen that the heterogametic 

 sex possesses one more chromosome than the other 

 instead of one less as in the XX : X type.^^® 



TABLE II 



Male Heterogametic and 

 Female Homogametic. 



Animals 



All Insects except 



Crustacea 



Arachnida 



Opisthogoneata 



Annelida 



Nematoda 



Echinodermata (as far as 



known) 

 All Vertebrates except. 



Female Heterogametic 

 AND Male Homogametic. 



those with haploid males 

 and the Lepidoptera and 

 Trichoptera ^*^' ®' 



161 



Some Fishes • 



Some Reptiles at any 



rate ^*** 

 All Birds ^". !«' 



Hexaploid Fragaria ela- 

 tior 101 



Plants 1" 



Rumex section Acetosa 



Humulus 



Melandriiim 



Populus 



Empetrum 



Elodea 



TABLE III 



Organisms with Sex -Determination by Male Haploid y 

 Insects : Rhynchota 



Some Aleurodidae I'l 

 Some Coccidae i*^' •* 

 Hymenoptera 



Probably all i". 172. 134 

 Coleoptera : Micromalthtis dehilia i** 

 Arachnida : Acarina (Mites) 



Some at least i«o. i" 

 Rotifera : Aslanchna 1®* 

 (Also possibly in some Thysanoptera) 



