446 E. ELEANOR CAROTHERS 



2. Heteromorphism, the supernumeraries and the reduction in num- 



ber of chromosomes 484 



3. Taxonom c variability and the gametic composition of the group. 486 



4. Correlation of chromosomal behavior and Mendelian principles... 487 

 V. Conclusion 401 



VI. Bibliography 492 



I. INTRODUCTION 



1 . Statement of the problem 



The present trend towards a closer correlation of the sub- 

 jects of cytology and genetics is one that promises much mutual 

 benefit, as is well demonstrated by the work of T. H. Morgan 

 and his co-laborers at Columbia University. While the present 

 work deals entirely with cytological data, the material prom- 

 ises much for a genetical study which, it is hoped, may be 

 undertaken later. 



Early in the course of his studies on Acrididian spermato- 

 genesis Dr. McClung outlined a general plan of study which, 

 it is hoped, will lead to a correlation between chromosomes and 

 body characters. This plan involves (1) a study of the chro- 

 mosomes of selected species of closely related genera; (2) a study 

 of numerous species within a genus; and (3) a study of the 

 details of organization of the chromosomes of certain species. 



In pursuance of this plan McClung has worked on the genus 

 Hesperotettix; Nowlin, taking up the genus Melanoplus belong- 

 ing to the same group, ha-s published ('08, '14) her results on 

 five species of this genus; Robertson ('16) has carried on work 

 on the Tettiginae; Pinney ('08) and Wenrich ('16) have studied 

 the genus Phrynotettix; and the writer has begun work on 

 the genus Trimerotropis — subfamily Oedipodinae. 



It is my purpose to confine this paper as closely as possible to 

 its own special topic. Two hypotheses, put forward by Van 

 Beneden ('83) and elaborated by Boveri ('88, '02) are, however, 

 essential to an interpretation of the facts presented. The first, 

 that of the individuality of the chromosomes, also supported 

 by Rabl ('85), has been actually demonstrated for the individual, 



