8o 



Edmund B. Wilson 



individuals have been sectioned) and is shown both in camera 

 drawings and in photographs. Eight of the latter are shown 

 (Photos 24 to 31), and these same groups are also represented in 

 the drawings, Text Figs. 2, a, b, c, d, e, j, k, I, together with four 

 others (/, g, h, i), also from photographs. Inspection of these 

 photographs and drawings will show that the unpaired idiochro- 

 mosome is at once recognizable by its large size, which renders 





Fig. I. Spermatogonia! groups of Pyrrochoris apterus (drawn on photographic enlargements, as 

 explained under Fig. i); a, b, c, d, e, j, k and / are reproductions of Photos 24, 25, 26, 27, 28, 29, 30 

 and 31, respectively. 



it almost as conspicuous as in Protenor (heretofore described by 

 Montgomery and myself). I find the size relations not quite the 

 same as Gross describes them. There are, as he states, eight 

 chromosomes that are considerably smaller than the others; but 

 two of the others are but slightly larger. The remaining twelve 

 paired chromosomes are much larger, though the contrast is 

 in my material not so great as Gross figures it. The idiochromo- 



