Kansas IInifersity Science Bolletin. 



Vol. IV, No. 12. SEPTEMBER, 1908. l^orx^v^^?:^?/ 



Vol. XIV, No 12 



THE CHROMOSOME COMPLEX OF MELANOPLUS 



BIVITTATUS SAY. 



BY NADINE NOWLIN. 



(rontribution from the Zoological Laboratory, Xo. 17!).) 



Plates XVI, XVII. 



THAT certain chromosomes are distinct individuals and 

 maintain their identity through the different generations 

 from spermatogonia to spermatids there can now be no doubt. 

 The work on the accessory chromosome, and very recently that 

 on the idiochromosomes, has furnished specific evidence of this. 

 Moreover, the complex as a whole has been studied and the in- 

 dividuality of most of the chromosomes of the group has been 

 fairly well established. For instance, Sutton ('02) carefully 

 measured the chromosomes of the Brachystola magna complex. 

 Baumgartner ('04), in his work on the cricket germ-cell, has 

 laid stress on the individuality as expressed in form, and Bo- 

 veri ('02) showed experimentally a difference in function. 

 Perhaps the most conclusive evidence of chromosome indi- 

 viduality is the occurrence of the same number in an entire 

 family, as found by McClung ('05) in the Acrididm. 



Chromosomes may exhibit individuality then (1) in size, 

 (2) in form, (3) in function, (4) in constancy in number. 

 To these might now be added another, (5) individuality ex- 

 pressed in grouping. McClung ('05), in his recent work on 

 certain species of Hesperotettix and Mermiria, discovered a 

 grouping or association of definite chromosomes that holds not 

 only for the individuals of a species, but for all the species of 

 the genus thus far investigated. Such an aggregation of chro- 

 mosomes he calls a multiple, and by careful measurement of 

 the elements of the multiple he finds that the specific difference 



(265) 



