EXPLANATION OF PEATE. 
All figures are photographs of sections and are magnified about one 
hundred fifty diameters. They have been slightly retouched with the 
pencil, for the purpose of adding to the distinctness of certain teatures. 
Nothing has been added with the pencil to that which was visible in the 
original photographs. 
REFERENCE LETTERS FOR ALL FIGURES. 
ad—adhesive organ (crescent). 
al—alimentary canal. 
b—button. 
bv—blood-vessel. 
c—cavity in hypophysis. 
h—heart. 
hy—hypophysis. 
hy’—posterior lobe of hypophysis. 
in—infundibular region of brain. 
m—position of future mouth opening. 
me, me’—mesenchyme. 
n—notochord. 
np—neuropore. 
st—stomodeum. 
s. v.—saccus vasculosus. 
Fic. 1—A median longitudinal section (sagittal) of an Amia embryo of 
the stage of the one shown in Fig. 1 of the preceding article. 
Fic. 1a—An approximately longitudinal section of an embryo somewhat 
younger than the one represented in Fig. 6 of the preceding article. 
Fic. 2a—A median longitudinal section of an embryo a little older than 
of the preceding article. 
Fic 2a.—A median longitudinal section of an embryo a little older than 
the one represented in Fig. 6 of the preceding article. 
Fic. 3—A median longitudinal section of an embryo still a little older 
than that shown in Fig. 6 of the preceding article, and older than the last. 
Fic. 4.—A median longitudinal section of the hypophysis and surround- 
ing structures of an embryo of the hatching stage (Fig. 8 of the preceding 
article). 
Fic. 5.—A longitudinal section of the hypophysis and surrounding tissue 
of a larva of Amia, 22 mm. long, taken a little to one side of the median 
plane. 
Frc. 6—A median longitudinal section of the hypophysis and surround- 
ing tissue of a larva of Amia, 22 mm. long. 
