THE KANSAS UNIVERSITY 

 SCIENCE BULLETIN. 



Vol. X, No. 14.] January, 1917. [toITx%^o\\. 



Chromosome Studies IV: 



AJDeficient Supernumerary Accessory Chromosome 



in a Male of Tettigidea parvipennis. 



W. REES BREBNER ROBERTSON, 

 University of Kansas. 



THE normal number of chromosomes of the species of Tetti- 

 gklde ("grouse locusts") so far examined is thirteen and 

 fourteen in the male and female, i. e., twelve autosomes and 

 either one or two X-chromosomes, respectively. (Robertson 

 *16 ; Rayburn, '17.) The subject of this investigation is a spec- 

 men which possesses the secondary sexual characters of a male, 

 yet has fourteen chromosomes. What makes the case still more 

 striking is the fact that the extra chromosome is probably an 

 X-chromosome. On measurement, however, it was found to be 

 shorter than' its mate by between one-fifth and one-fourth the 

 normal length (figs. 15, 17, etc.). As will be seen, it is prob- 

 ably to be considered a supernumerary, but deficient, accessory- 

 chromosome. 



Its occurrence in the individual is uniform for all cells found 

 dividing, so7?iatic or germinal. In somatic cells it is not so 

 readily identified in every case yet the fact that the number 

 fourteen may always be clearly counted indicates its presence 

 when other means fail. The somatic cells found containing 

 it were from "fat body," follicle wall, and vasa efferentia 

 tissues. The chromosomes in these cells are large and widely 

 separated. The drawings indicate their actual positions in 

 most cases (figs. 1 to 5). No difficulty or doubt was had in 

 making the count here. Of course, counts in somatic cells 

 could be obtained only from tissues surrounding the testes, 



(275) 



