MULTIPLE CHROMOSOMES 521 



mens they reach conclusions regardmg the relationships of indi- 

 viduals and groups which are soundly based upon well defined 

 external characters and upon personal knowledge of the habits 

 and distribution of the materials. Working quite independently 

 of them I reach conclusions regarding the relationships of indi- 

 viduals and groups from the study of their germ cells and, in 

 most cases, find that there is no difference in our estimate of 

 these relationships. Since the discrimination between nearly 

 related forms, upon cytological characters, sometimes reveals 

 groupings that have been overlooked by earlier taxonomists, the 

 feeling of confidence in the validity of the theories upon which 

 such determinations are made is much strengthened. I feel con- 

 fident that a full agreement between cytology and taxonomy de- 

 pends only upon the quality of the criteria of differentiation 

 and upon the accuracy of observation on the part of the followers 

 of these two methods of gaining a knowledge of the organization 

 of biological units of different degrees of complexity and extent. 



II. CHROMOSOME CONDITIONS IN THE GENUS HESPEROTETTIX 



1 . General observations . 



When the observations on Hesperotettix were first announced 

 I had only a few specimens, and, because of unfamiliarity with 

 taxonomic characters, my assistants failed to distinguish the 

 species and confused the sources of the material used for study. 

 It was only when the germ cells were examined that it became 

 apparent that all the specimens regarded as H. viridis did not 

 belong to that species. Later and more careful collections 

 enabled me to determine that H. viridis and H. pratensis were 

 both represented. No difficulty is now experienced m discrim- 

 inating between these species by germ cell characters. Together 

 with H. speciosus, these represented the full extent of my ac- 

 quaintance with the genus. Although the chromosome complex 

 was, in its major features, consistently afike in the three species, 

 I pubhshed no further observations, because I hoped to obtain 

 preparations from the other North American forms in order to 

 make the presentation complete. After waiting a number of 



