EXPLANATION OF PLATES. 



The drawings in plates 1 to 9 were in all cases made with the aid of a camera 

 lucida, using a Zeiss No. 12 compens. ocular and a Spencer homogeneous 

 immersion 1.8 mm. objective, N. A. 1.30. Drawings no. 63-65 were made at a 

 magnification of 2,600 diameters, all the others at a magnification of 3,000 

 diameters. The drawings have been reduced one third in reproduction. 



Plate 10 consists of photomicrographs made at a magnification of 1,150 

 diameters. 



Symbols used: 



A designates selected chromosome-pair "A." 



D (( « « u li r> >> 



"C". 



X " accessory chromosome. 



G " composite granule. 



g ** polar granule. 



