190 



Embryogenesis: Preparatory Phases 



of the egg and is then no longer readily 

 visible. It has been claimed (Hartmann 

 et al., '40) that the jelly coat dissolves under 

 the influence of such extracts. However, 



shown it to be an acidic protein, isoelectric 

 at pH 3, and containing about 16 per cent 

 nitrogen. Hultin ('47a, b) considers the 

 active principle to be a basic protein. This 



Fig. 60. Eggs of the sea urchin Lytechinus pictus. a, b, c, and d. Successive pictures of the same egg at 

 about % minute intervals after addition of a solution of antifertilizin, showing formation of the precipitation 

 membrane and its contraction to the surface of the egg; X 400. e and /, Successive pictures of the same egg 

 and an adjacent isolated jelly-hull at 1 minute and 20 minutes, respectively, after addition of antifertilizin, 

 showing the persistence of the material of the isolated jelly-hull at the time when the precipitation membrane 

 has contracted to the egg's surface and has become indistinguishable from it; X 350. g and h, Successive pic- 

 tures of the same fertilized egg at 1 minute and 3 minutes after addition of antifertilizin. i and /, Successive 

 pictures of the same fertilized egg in 2-cell stage at 1 minute and 4 minutes after addition of antifertilizin; 

 X 350. (From Tyler, '49.) 



tests with isolated jelly hulls (see Fig. 

 60e, /) show that the precipitation mem- 

 brane persists long after it has reached the 

 surface in the control eggs. 



Chemical studies on antifertilizin (Tyler, 

 '39a, '40b, '48a; Runnstrom et al., '42) have 



contention is refuted by Metz ('49) who had 

 earlier ('42a) found that basic proteins from 

 sea urchin sperm have antifertilizin-like ef- 

 fects, but, in contrast to the above anti- 

 fertilizin preparations, they also agglutinate 

 sperm. 



