ON THE MORPHOLOGY OF THE CHROMOSOME 

 GROUP IN BRACHYSTOLA MAGNA. 



WALTER S. SUTTON. 



The appearance of Boveri's recent remarkable paper l on the 

 analysis of the nucleus by means of observations on double-fer- 

 tilized eggs has prompted me to make a preliminary communica- 

 tion of certain results obtained in a general study of the germ-cells 

 of the great "lubber grasshopper," Brachystola niagna. 



As will appear from a glance at the figures given in my former 

 paper 2 upon the same form, the cells of Brachystola, like those 

 of many amphibia, selachians and insects and certain of the flow- 

 ering plants, exhibit a chromosome group, the members of which 

 show distinct differences in size. Accordingly, one feature of 

 this later study has been a critical examination of large numbers 

 of dividing cells (mainly from the testis) in order to determine 

 whether, as has usually been taken for granted, these differences 

 are merely a matter of chance, or whether, in accordance with 

 the view recently expressed by Montgomery, 8 in regard to a cer- 

 tain pair of elements in the nuclei of one of the Hemiptera, char- 

 acteristic size-relations are a constant attribute of the chromo- 

 somes individually considered. With the aid of camera drawings 

 of the chromosome group in the various cell-generations, I will 

 give below a brief account of the evidence which has led me to 

 adopt the latter conclusion. 



In the first generation of secondary spermatogonia, which are 

 the earliest germ-cells I have been able to obtain in Brachystola, 

 certain differences in length and volume are to be seen between 

 the members of the chromosome group. These cells, as shown 

 in my former paper already referred to (where they are errone- 



1 Boveri, Th. (1902), " Mehrpolige Mitosen als Mittel zur Analyse des Zellkerns," 

 Verh. d. Phys. Med. Ges. zu Wiirzburg, XXXV. 



2 Sutton, W. S. ( 1900), " The Spermatogonial Divisions in Brachystola magna," 

 Kans. Univ. Quart., Vol. 9. 



3 Montgomery, T. H., Jr. (1901), "A Study of the Chromosomes of the Germ 

 Cells of the Metazoa," Trans. A met: Phil. Sof., Vol. XX. 



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