BEHAVIOR OF THE GAMETES 227 



is present and that it is associated with the jelly layer around the egg. Tyler 

 ('41 ) concludes: 



( 1 ) When fertilizin is present in the form of a gelatinous coat around the 

 egg, it enhances fertilization; 



(2) when present only in solution around the egg after the gelatinous coat 

 is removed, it hinders fertilization by agglutinating the sperm; and 



(3) that fertilizin is not entirely essential since eggs can be fertilized when 

 the jelly coat is removed, but a greater number of sperm are needed 

 under these circumstances. 



Tyler also has detected antifertilizin below the surface of the egg and by 

 crushing the eggs was able to show that antifertilizin from the interior of the 

 egg is able to neutralize the fertilizin of the jelly coat surrounding the egg 

 (Tyler, '40, '42). In Germany, Hartmann and his associates (see Hartmann, 

 M., et al., '39, a and b, '40) have demonstrated that by exposing fertilizin 

 to heat or light one may separate the "agglutinating factor" from the "acti- 

 vating factor." Heat at 95° C. destroys the "agglutinating factor," while ex- 

 posure to bright light causes the "chemotactic" and "activating" factors to 

 disappear. The factual presence of the egg products, fertilizin and antifertilizin, 

 postulated by Lillie thus is well established. 



Fertilizin appears to be widely distributed as an egg secretion among ani- 

 mals, invertebrate and vertebrate. Among the latter it has been identified in 

 cyclostomes, certain teleost fishes, and in the frog, Rana pipiens (Tyler, '48). 

 Moreover, it is becoming increasingly clear that the term, fertilizin, as em- 

 ployed originally by F. R. Lillie, includes more than one secretion. How many 

 separate enzymes or other substances may be included under the general terms 

 of fertilizin and antifertilizin remains for the future to determine. Moreover, 

 the exact presence of particular gynogamic substances in the egg secretions 

 of different animal species may vary considerably. For example, the sperm- 

 activating principle may not be present in all animal species. In fact, there 

 is good evidence to show that it is not present, for example, in all species 

 of sea urchins. 



Fig. 117. Fertilization and maturation of the egg in Amphioxus. (A, B, H after Cer- 

 fontaine, '06; C-1 after Sobotta, 1897.) (A) Metaphase of first maturation division 

 before sperm entrance. (B) Anaphase of first maturation division before sperm entrance. 

 (C) First polar body and metaphase of second maturation division befoie sperm entrance. 

 Observe the first or primary fertilization membrane. (D) Sperm has entered near vegetal 

 pole of egg. (E) Outer egg membrane has enlarged and is now much thinner; the 

 second egg membrane is separating from the egg, and the second polar body is forming. 



(F) Outer and inner egg membranes have fused and expanded; pronuclei of sperm and 

 egg are evident; the sperm aster is to be observed in connection with the sperm nucleus. 



(G) Meeting of the two pronuclei between the developing amphiaster. (H) Fusion 

 nucleus complete. (1) Diploid chromosomes now evident preparatory to the first 

 cleavage of the egg. 



