MENDELIAN RATIO AND CHROMOSOMES 505 
EXPLANATION OF PLATES 
All figures are from camera lucida outlines. Original magnification 2400 diam- 
eters. Actual magnification of figures 1200 diameters. 
Numbers 21 and 22, spermatids, are displaced from the position they would 
occupy in order of development for purposes of comparison; the others are arranged 
as nearly as convenient in that order. 
All drawings are from B. magna unless otherwise indicated. Ordinary chrom- 
osomes are in outline for clearness of comparison. 
Accessory at upper pole except figures 43 and 55. 
