212 
CHARLES L. PARMENTER 
mental and personal error of about 0.6 mm. at his magnification. 
This, of course, is negligible in comparison with the large errors 
arising from foreshortening in numerous chromosomes. 
Concerning the favorableness of the spermatogonial chromo¬ 
somes for measurement, Meves says (p. 274) that by no means 
do all of the chromosomes lie in the equatorial plane; without 
exception the bend lies in the plane while the ends lie outside; 
in the drawings such chromosomes seem shortened and therefore 
the measurements upon these chromosomes would give only an 
approximate value. Judging from these statements and from 
the magnitude of error due to the slight foreshortenings in my 
material, his measurements very likely contain errors which 
amount to as much as 4 or 5 mm. 
For measurements of somatic chromosomes he chose (p. 280) 
polar views of the transformation stages between the prophase 
and metaphase stages in the epithelium of the gill plates (figs. 16 
to 18) and extraordinarily well-flattened polar views of pro¬ 
phases (figs. 11 to 13) and metaphases (figs. 14 to 15) in the 
peritoneum. In the three prophases of the peritoneum the chro¬ 
mosomes lay nearly or entirely parallel with the upper surface 
of the cell. According to this description, it is evident that these 
three prophases are the most favorable cells, and even in these 
the chromosomes are not entirely free from foreshortening. The 
chromosomes of the other cells probably were more foreshortened. 
Therefore, judging from results in Ambystoma, his measurements 
contain errors due to foreshortening which probably vary from 2 
to 5 mm. 
The amount of the errors which are due to the twisting of the 
chromatids of these chromosomes is uncertain. Such twisting is 
evidently present, as indicated by the irregular contour of his 
chromosome drawings which are similar to those of my own. 
The errors due to this twisting may largely neutralize each other 
as explained above (p. 189). He mentions also the possibility of 
different rates of contraction of the chromosomes, especially in 
the earlier stages. Having before us the conditions under which 
Meves made his measurements, we are in a position to judge 
their value more or less correctly. 
