14 
Psyche 
March 
The endochorion is hardly ever loosened at all from the 
yolk and no vitelline membrane has been found between 
them. Heymons (1897) reported a vitelline membrane in 
Lepisma saccharina, but Uzel (1898), who studied the eggs 
of the same lepismatid, did not mention it. 
Between the exochorion and the endochorion at the an- 
terior end of the egg is the micropylar area, a circular 
thickening about 280 microns in diameter (Fig. 5). The 
thickening consists of as many as twenty or more concentric 
lamellae, each about as thick as the exochorion, with which 
the thickening is identical in staining reactions and to which 
it adheres if the latter becomes loosened from the endo- 
chorion. The thickening is thinner peripherally than cen- 
trally, since not all of the lamellae extend to the margin 
of the area. 
In the micropylar area are found three small infundibular 
depressions which, if connected, would form the corners 
of an equilateral triangle. Two of the depressions are shown 
in figure 5 (DP). The depressions, which can rarely be 
demonstrated to penetrate the micropylar thickening com- 
pletely, are filled with folds of the exochorion and with the 
chorionic droplets described above. There sometimes ap- 
Explanation of Plate 2 
All figures represent portions of sections. Fixative: Maximow’s. Stain: 
Feulgen’s all figs, except 2 and 5; Mallory’s triple, figs. 2 and 5. Magnifi- 
cations approximate. Fig. 1. 20 minute old egg, showing sperm head ac- 
cumulating cytoplasm, 400 x. Fig. 2. 30 minute old egg, showing egg nucleus 
in anaphase of first maturation division, 500 x. Fig. 3. 2% hour old egg, 
showing egg nucleus in anaphase of second maturation division, 500 x. 
Fig. 4. 75 minute old egg, showing late telophase of first maturation divi- 
sion; secondary oocyte nucleus forming in upper left, first polar body in 
lower right; 500 x. Fig. 5. Longitudinal section through micropylar (an- 
terior) end of 2 hour old egg, 160 x; CD, chorionic droplet; DP, depres- 
sion; EN, endochorion; EX, exochorion; EXT, exochorionic thickening. 
Fig. 6. 90 minute old egg, showing late stage in the contraction of the 
sperm head, 1250 x. Fig. 7. Egg about 2 hours old, showing male pronuc- 
leus during its growth period; 1875 x. Figs. 8-11. 3 to 4 hour old eggs, 1250 
x. Fig. 8. Early stage of union of male and female pronuclei. Fig. 9. Female 
pronucleus shown near top just enteriing the sperm plasm; male pronucleus 
(below). Fig. 10. Female pronucleus (below) and male pronucleus (above) 
about to unite. Fig. 11 . Late stage of union of male and female pronuclei. 
