414 THE AMERICAN NATURALIST. 
EXPLANATION OF PLATE IV. 
Fic. 1. Section of entire egg in early cleavage phase, showing more ra apid 
rate at one pole, while the ic i a a pi eae nucleus and no indications of 
segmentation. Camera sketch, x abou 
2. Two-cell Fan At the le ee is hows a perfect nuclear spindle, s/, 
and in the opposite blastomere several asters, which may indicate the nuclear 
divisions which have occurred, without involving the cytoplasm. 
G. 3. Section of egg, X 135, showing various internal cleavage conditions, 
dud superficial; z, nuclei in resting conditio 
Fic. 4. Portion of egg more highly m nifio 4 
Fic. 5. Portion of another egg, Fue essentially similar conditions. 
Fic. 6. Section of egg at completion of segmentation, showing a mass of 
nuclei partially organized into a cellular ectoderm, ec. 
