272 WM. REES B. ROBERTSON 



numary chromosomes, and that according to all indications they 

 are permanent. 



The fact that three genera of Tettigidae show the same general 

 plan of chromosome structure leads us to suppose that within 

 each of these three genera we might look for the same general 

 sort of variations, such as could be dealt with by the Mendelian 

 law. Nabours ('14), in his work upon the inheritance of color 

 markings in Paratettix, has shown that their behavior conforms 

 to this law in one of these genera. He finds nine pure strains 

 showing distinct color patterns, and in addition to this eighteen 

 heterozygous patterns from combinations of these pure strains. 

 It is a striking fact that in collecting specimens of three other 

 genera, Acridium, Nomotettix and Tettigidea, I have found many 

 of the same markings. All of these genera have individuals 

 showing the white spot on the large femora which Nabours 

 has described in his Paratettix punctofemorata (fig. D, plate 

 VI). The spot varies slightly in shape and orientation, but 

 nevertheless it is a white spot on the same region of the rear leg. 

 Likewise I have found all four genera to have individuals with 

 a white band across the thorax, such as he has described in his 

 leucothorax variety (fig. C, plate XI) and as Hancock ('02) has 

 shown for Acridium (Tettix) in the fourth specimen of his figure 

 1, page 9. I have also found in all four genera the leuconotus 

 variety shown by Nabours at B, plate VI, and by Hancock in 

 figure 1, specimen 6. The variety with a median stripe of the 

 shape of that shown at E (Nabour's fig. VI), but white instead 

 of yellow, I have found in all four genera. Hancock has also 

 pictured this variety for Acridium in his figure 1. The gray 

 variety carrying small patterns of black, like A of Nabours and 

 the first specimen of figure 1 in Hancock, is probably the most 

 common of all patterns in all of the genera. 



The genera Nomotettix, Acridium and Paratettix belong to 

 the same subfamily (Tettiginae) , while Tettigidea belongs to an 

 entirely distinct subfamily, the Batrachidinae. The germ-cell 

 structure shows Tettigidea to be farther removed from the other 

 three genera than they are from one another. Basing my opinion 

 upon a knowledge of germ cells alone, I should expect to find in 



