56 Comparison of Characters 



IX. COMPARISON OF MUTANT CHARACTERS IN 

 D. VIRILIS WITH THOSE IN OTHER 

 SPECIES OF DROSOPHILA. 



Several species of Drosophila have now been studied sufficiently 

 to permit a comparison of their genetic behavior. With the excep- 

 tion of D. virilis and of the well-known D. melanogaster, these are 

 listed in table 7, together with references to the papers dealing with 

 them and a statement as to the number of mutant characters in each. 

 Their chromosomal relations may be determined by reference to 

 figures 1 and 2. By examining the table an estimate may be made 

 of the extent of the published information on the various species. 



In the following comparisons, unpublished as well as published 

 information has been drawn upon freely, with the consent of the 

 investigators, as mentioned on page 13 under "Acknowledgments." 



At the outset of a comparison of this kind, which seeks to detect 

 homologies, it is necessary to inquire as to what evidence is to be 

 considered reliable in the absence of direct hybridization tests. 

 As stated in the introduction, the failure of the above species to 

 hybridize (with one exception noted) presents a serious obstacle to 

 this particular feature of the work. 



