MECHANISM OF MEMBRANE FORMATION 211 
water is raised by the addition of some NaOH (e.g., 1.0 c.c. 
N/10 to 50 ¢.c. sea-water), the chorion is gradually dissolved 
in a number of eggs. The writer has recently found that the 
Fig. 64 Fig. 65 
Fics. 63-65.—Dissolution of the chorion surrounding the egg of Lottia 
gigantea, a mollusc, on treatment with saponin. Fig. 63 shows the egg before the 
treatment with saponin. c is the chorion. Fig. 64 shows the same egg a few 
minutes after the addition of saponin. The chorion c is greatly swollen and at 
the point of liquefaction. Fig. 65 shows the chorion having completely disap- 
peared and the egg become spherical. In this condition it is permeable for the 
spermatozoon. 
weak bases are much more efficient than the strong bases. 
Thus the amines and NH,OH will cause the swelling and lique- 
faction of the chorion of Loétia in the same concentration much 
more rapidly than the strong bases NaOH and tetraethyl- 
ammoniumhydroxide. 
