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.c. sea-water), the chorion is gradually dissolved 

 in a number of eggs. The writer has recently found that the 



Fig. 63 



Fig. 64 



Fig. 65 



FIGS. 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 haying 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 4 OH will cause the swelling and lique- 

 faction of the chorion of Lottia in the same concentration much 

 more rapidly than the strong bases NaOH and tetraethyl- 

 ammoniumhydroxide. 



