EXPLANATION OF PLATES 



The drawings were made with the aid of the camera lucida at a magnification 

 of 2400 diameters and have been reduced one-third in reproduction. 



Plates 1 to 10 show side views of first spermatocyte metaphases, arranged as 

 nearly as possible according to size. Each horizontal row represents one cell, 

 the vertical rows, corresponding chromosomes in different cells. They are so 

 arranged that the accessory, number 4, is always passing to the upper pole. 



The individuals from which drawings were made were numbered consecutively 

 from one to seventy-five. The same number always applies to the same speci- 

 men ; successive figures from any individual are indicated by letters. 



When supernumerary chromosomes are present they are placed at the left 

 of chromosome number 12 to indicate that they are out of the normal series and 

 especially because they would occupy no definite position in relation to size. 



Plate 14 is composed of photomicrographs made at a magnification of 1140 

 diameters and reproduced without reduction. 



PLATE 1 



EXPLANATION OF FIGURES 



Lateral views of first spermatocyte complexes from a single individual (no. 

 1), showing mode of segregation of three heteromorphic tetrads (chromosomes 

 no. 1, 7, and 8. 



6 to e Alternate distribution of atelomitic dyads of chromosomes number 

 7 and number 8. 



/ and g Concurrent distribution of same homologues segregating opposite 

 the accessory. In / the atelomitic dyad of chromosome number one is accom- 

 panying the similar dyads of chromosomes number 7 and 8, while in g it is 

 passing to the opposite pole. 



h and i Same as / and g except that atelomitic dyads of numbers 7 and 8 are 

 passing to the same pole as the accessory. 



494 



