VARIATIONS IN THE SIZE OF CHROMOSOMES. 



FRANK A. HARTMAN. 



OUTLINE OF CONTENTS. 



I. Introductory 226 



II. Material 226 



III. Observations 227 



1. Comparison of the size of chromosomes 227 



(a) Chromosomes of nymphs compared with those of adults 227 



(6) Comparison of chromosomes of different cells of the same 



individual 228 



2. Causes of chromosome size variations 228 



(a) Unequal growth 228 



(6) Unequal division 229 



IV. Discussion 230 



1. Chromosome variations and their causes 230 



2. The role of chromosome variations in heredity. Theoretical 230 



V. Conclusion. The facts and the theory which they suggest 231 



I. INTRODUCTORY. 



From the time that the importance of germ cell chromosomes 

 was first realized, the mass of investigation on this subject has 

 dealt with the development of the chromosomes. Practically 

 nothing on a comparison of chromosomes of the same species 

 has been published. Therefore these results are given that 

 they may throw some light on the behavior of chromosomes. 



The observations in this paper, although somewhat limited, 

 suggest interesting theoretical considerations. 



Further investigations are being made by the author to test 



these ideas. 



II. MATERIAL. 



All of the material is of the species Schistocerca americana, 

 with the exception of one specimen which is S. alutacea. A brief 

 description of the material follows. 



Young Nymphs. Out of a number of nymphs, collected at the 

 same time and place near the Kansas University campus, nine 

 were taken at random. These were probably of the same age, 

 for they were of approximately equal size, ranging from 12 to 14 



mm. in length. 



226 



