EXPLANATION OF PLATES 
The drawings of plates 1 and 2 were outlined with an Abbe camera lucida at a 
magnification of 3900 diameters obtained with a Leitz 2 mm. oil-immersion ob- 
jective and a Zeiss X 18 compensating ocular, with draw-tube set at 150 mm. and 
drawing made at the level of the base of the microscope. In the process of 
reproduction, they have been reduced one-third, and therefore appear at a magni- 
fication of 2600 diameters. The numerals affixed to the chromosomes indicate 
their relative sizes, the smallest being numbered ‘1.’ 
PLATE 1 
EXPLANATION OF FIGURES 
1toS8 Tettigidea parvipennis 
1 Chromosomes of an oogonial cell; female. 
2 First spermatocyte; tetrad No. 4 is normal; No. 5 is the sex-chromosome ; 
male. 
3 Chromosomes of a first spermatocyte of a third animal (male) showing a 
normal No. 4 tetrad; No. 5 and No. 2 seen somewhat foreshortened. 
4to8 From a fourth animal, male. 
4 Chromosomes of a spermatogonium; all chromcsomes are split and in meta- 
phase; one of the chromosomes of pair No. 4 is deficient. 
5 First spermatocyte; the deficient No. 4 (4—) separating from its mate (4). 
6 First spermatocyte; deficient No. 4 (4—) in abnormal, oblique contact 
with its mate (4). 
7 Deficient No. 4 tetrads taken from three other first spermatocyte dividing 
cells in the same animal, showing uniform size but variation in manner of con- 
tact of the conjugating chromosomes. 
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