INEQUALITIES IN HOMOLOGOUS CHROMOSOMES LEE 
Since the diameters of the chromosomes are uniform through- 
out the series in any given cell, the relative sizes can be learned 
best by measurement of lengths. My measurements have been 
made from drawings outlined by means of a camera lucida, the 
image being projected at the level of the base of the microscope. 
A 2 mm. Leitzoil-immersion objective and an 18 X Zeiss com- 
pensating ocular were used for outlining. I feel reasonably 
certain that my drawings show approximately the correct 
relative sizes of the chromosomes in each cell. 
The average length (doubled) of the No. 3 chromosomes in 
the figures (x 2600) of six cells from two normal individuals 
of Tettigidea parvipennis is 15 mm. The average length of the 
No. 4 chromosomes under the same conditions in the same six 
cells is 17.05 mm. The ratio of the No. 3 to the No. 4 chromo- 
somes is therefore as 1 to 1.14. This may be taken as approxi- 
mately the normal size relation of the No. 3 and No. 4 chromo- 
somes; that is, No. 4 is about one-seventh longer than No. 3. 
In figures 4 to 8 are cells from a male individual of the same 
species, In which one member of the No. 4 pair of chromo- 
somes (4—) is abnormally small. The average length of the No. 3 
tetrad is here 13.1 mm. This is shorter than in the preceding 
case of six cells, but in this instance all chromosomes are affected 
similarly, the reduction in size being due probably to the cells 
having been in slightly different stages when killed. This does 
not affect the relative lengths of the chromosomes, however. 
The average (doubled) length of the larger (no. 4) diad (figs. 5-8) 
in the same cells is 15.5 mm. The ratio therefore of the No. 3 
tetrad in these cells to the larger diad of the abnormal No. 4 
tetrad, or to a No. 4 tetrad made up of two such diads, would 
be as 1 to 1.18; 1.e., the ratio of the No. 3 chromosomes to the 
normal member of the No. 4 pair here is as 1 to 1.18. This 3s 
not far from the normal ratio, 1.14, and the difference is quite 
within the range of the probable error due to inaccurate measure- 
ment, etc. But the average (doubled) length of the smaller diad 
of the abnormal No. 4 tetrad is 12.7 mm., instead of 15.5 mm. 
The ratio therefore of the No. 3 tetrad to a tetrad made up of 
two such No. 4 diads would be as 1 to 0.97; 1.e., the ratio of the 
