186 



WM. REES B. ROBERTSON 



7. Lateral lobes rounded, not angular 



(figs. 3, 5, lob.l). 



8. Eyes rounded rectangular, long 



diameters almost parallel (figs. 

 3, 4, 13a, 13b). 



9. No supra-ocular lobe of vertex 



extending over eyes. 



7. Lateral lobes angulate (fig. 9, lob. 1)' 



8. "Eyes elongate-triangular (figs. 10, 



11), long diameters forming an 

 angle of 90° (figs. 10, 11). 



9. Eyes partly covered by small supra- 



ocular lobes of vertex (figs. 10, 11, 

 lob. su'oc). 



Within the subfamily Tettiginae the genera Acridium and 

 Paratettix differ in the following respects: 



Acridium (Tettix) 



1.' Vertex much broader than one of 

 the eyes, projects beyond them 

 (figs. 3, 4), angulate anteriorly. 



2. Eyes small. 



3. Pronotum does not project far over- 



head, does not reach posterior 

 margin of eyes (figs. 3, 4). 



4. Anterior margin of pronotum slight- 



ly angulate. 



5. Body between shoulders not so 



wide as in Paratettix. 



Paratettix 



1. Vertex as narrow as, or very slightly 



wider than, one of the eyes (figs. 

 13a, 13b), does not project be- 

 yond, truncate anteriorly. 



2. Eyes large, bead-like. 



3. Pronotum projects far overhead, 



reaches posterior margin of eyes 

 (figs. 5b, 6, 13a, 13b). 



4. Anterior margin of pronotum decid- 



edly truncate (figs. 5b, 6). 



5. Body between shoulders wide (figs. 



5b, 6). 



Within Acridium (Tettix) I have studied four species. As 

 in the case of the genera compared above, two of these species 

 are more closely related to each other than either of them is 

 to the third, obscurus. Of ornatus I have not a sufficient num- 

 ber of drawn cells to justify comparison of body characters with 

 those of the other species. (See opposite page.) 



By studying these characters it will be seen that granulatus 

 and incurvatus usually agree more closely with each other than 

 with obscurus. 



THE CHROMOSOMES 



Within the cell, the varying degrees of relationship which we 

 have been looking at from a taxonomic point of view are again 

 shown to a surprising extent by chromosomes. This is found 

 in the constancy of numbers and in differences between size 



