£22 THE AMERICAN MIDLAND NATURALIST. 
FIGURE 12. : 
An edge view of the spiral nebula HV 24, Comae Berenices, showing 
that it has a highly discoidal form. The dark band that shows across 
the central ball is probably caused by light-absorbing matter. The fact 
that spiral nebula are discoidal in form supports the hypothesis that the 
solar system, also discoidal, is descended from one of them. Photo- 
graphed at the Lick Observatory. From Chamberlin, University of 
Chicago Press, 
