324 C. E. MCCLUNG. 



Much has been done lately to show that the theory of the in- 

 dividuality of the chromosomes is well founded, but up to this 

 time all that has been attempted has been to prove that in the 

 species there is a constant series of chromosomes that appears 

 in the successive generation of cells in each individual. I think 

 that this has been done beyond reasonable question, in a number 

 of forms and by different means. From the brief comparative 

 study of the Acrididae that I present here it now appears that not 

 only are the chromosomes constant for the species, but also for 

 the genus and family. 



The far-reaching importance of this correlation between somatic 

 characters and germ cell structure is at once apparent, for there 

 is now some hope that it will be possible to establish the relations 

 that exist between body characters and individual chromosomes. 

 This has been the goal toward which I have been working ever 

 since I observed the constancy in the behavior of the accessory 

 chromosome and surmised its connection with the development 

 of the male sexual characters --the first attempt, so far as I 

 know to establish a relation between a particular chromosome 

 and the same group of characters in different species. 



The problem is unquestionably one of great complexity and 

 difficulty, but I believe that with careful comparative studies of a 

 great number of genera the role of the individual chromosome 

 in development can be ascertained. If it is found possible, as I 

 hope it may be, to apply experimental methods in breeding, etc., 

 to these forms the results may be more quickly brought about. 

 I have already made some tentative experiments, but have as yet 

 accomplished nothing definite. Increased knowledge of the phe- 

 nomena prevailing in these animals is bound to make the corre- 

 lation between germ cell architecture and body characters more 

 and more definite in details, and in connection with observations 

 on other forms, will permit the formulation of some general prin- 

 ciples that will be applicable to all organisms. 



In the present state of our knowledge, however, we can do 

 little more than erect a working hypothesis of a very general 

 character, which doubtless will have to be modified with the ap- 

 prehension of new groups of facts. It is to be borne in mind 

 that our hypothesis must explain not only the appearance of the 



