CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE MUSEUM OF COMPARATIVE ZOOLOGY AT 
HARVARD COLLEGE. NO. 256. 
CHROMOSOME STUDIES 
TIl. INEQUALITIES AND DEFICIENCIES IN HOMOLOGOUS 
CHROMOSOMES: THEIR BEARING UPON SYNAPSIS 
AND THE LOSS OF UNIT CHARACTERS 
W. REES BREMNER ROBERTSON 
FOURTEEN FIGURES (THREE PLATES) 
In November, 1910, while preparing a larger paper upon the 
problem of synapsis in the germ cells of certain grasshoppers 
belonging to the subfamily Tettigidae (Robertson 715), I found 
some individuals in which there occurred a pair of unequal 
homologous chromosomes. I made a series of drawings of these 
pairs at the time, intending to incorporate them later into my 
larger paper. That paper is not yet completed, owing to the 
duties of teaching during the last year at Kansas University. 
The importance of these inequalities in members of a chromosome 
pair, however, seems to warrant publishing the results in brief 
form. In this account I wish to point especially to a possible 
relation between these unequal chromosomes and the behavior 
of certain unit characters in breeding; also to the bearing which 
the permanency of such chromosomes has upon the problem of 
parasynapsis. 
In the Tettigidae, a subfamily of the short-horn grasshopper 
family Acrididae, I have found, for all the species of at least 
four different genera which I have examined, the number of 
chromosomes to be uniformly 14 in the female (figs. 1, 11) and 
13 in the male (figs. 4, 9). I have also found all to have, with 
limited variation, among the autosome (ordinary chromosome) 
series, two extremely long pairs of chromosomes, the 7’s and 6’s 
(figs. 1, 3, 4), two intermediate pairs, the 4’s and 3’s (figs. 1-3) 
or 5’s and 4’s (figs. 9, 10), and two very small pairs, the 2’s and 
1’s (figs. 1-3, Tettigidea) or the 3’s and 2’s (figs. 9-10, Acridium). 
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