Reprinted from JOURNAL OF MORPHOLOGY, VOL. 22, No. 1 

 MARCH, 1911 



STUDIES ON CHROMOSOMES 



VII. A REVIEW OF THE CHROMOSOMES OP NEZARA; WITH SOME 

 MORE GENERAL CONSIDERATIONS 



EDMUND B. WILSON 



From the Zoological Department, Columbia University 



NINE FIGURES AND ONE PLATE 



CONTENTS 



Introduction 1 71 



Descriptive 73 



1 The second spermatocyte-division in Nezara 73 



a The idiochromosomes 73 



b The double chromosome 77 



2 The first spermatocyte-division 78 



3 The growth-period and spermatocyte-prophases 80 



4 The diploid chromosome-groups 83 



General 84 



5 The idiochromosomes 84 



a Composition and origin of the XY-pair 85 



b Modifications of the X-element 88 



c Sex-limited heredity 94 



d Secondary sexual characters 99 



6 Modes in which the chromosome-number may change 99 



Conclusion 105 



INTRODUCTION 



In the first of these 'Studies' ('05a) I described the idiochromo- 

 somes (X and Y-chromosomes) of Nezara hilaris as being of equal 

 size in the male, and reached the conclusion that in this species 

 no visible dimorphism appears in the spermatid-nuclei. In my 

 third 'Study' ('06), after examination of the female diploid groups, 

 this species was assigned a unique position as the single then 



71 



