BEHAVIOR OF THE GAMETES 229 



Study since the initial endeavors of Fieri in 1899. In recent years, three gen- 

 eral types of substances have come to be recognized in relation to the sperm 

 of different species. These three groups of substances are: 



( 1 ) secretions which cause lysis, 



(2) a substance or substances related specifically to the fertilization reac- 

 tion (i.e., egg and sperm contact), and 



(3) substances which bring about the spawning reaction in the female. 



a) Secretions Producing Lysis. To cite the importance of lytic sub- 

 stances produced by the sperm, reference is made first to the situation in the 

 amphibian, Discoglossus pictus. In this primitive anuran, the sperm, although 

 about 2 mm. long, are almost incapable of motility. However, they do ac- 

 cumulate in the region of a thickened portion of the egg capsule which overlies 

 a depressed area of the egg. They are capable of passing through this thickened 

 area of jelly by the aid of a digestive enzyme probably associated with the 

 acrosome (Hibbard, '28). Hibbard also suggests that "nuclear fluids" accu- 

 mulate in the bottom of the egg depression and these fluids attract the sperm 

 to the thickened area of the capsule. If so, here is an example of two chemical 

 substances, one elaborated by the egg and the other by the sperm, both work- 

 ing together to bring about fertilization. In substantiation of Hibbard's views 

 of the presence of a lytic enzyme associated with the sperm of this species, 

 Wintrebert ('29) found that extracts from the sperm contained an enzyme 

 which is capable of digesting the inner jelly coat of the egg. 



More recently, Tyler ('39) has found that sea-water extracts of frozen 

 and thawed sperm of two mollusks (Megathura crenulata and Haliotis crache- 

 rodii) were able to dissolve the egg membranes of the respective species. 

 Cross-species reactions were not obtained, however. Strong extracts of con- 

 centrated sperm suspensions bring about egg-membrane disappearance in less 

 than one-half minute, but with the jelly coat present around the egg it takes 

 about three minutes. Also, Runnstrom and his collaborators ('44, '45, a and 

 b, '46) made methanol extracts of sea-urchin sperm which were able to liquefy 

 the superficial cortical area of the egg. 



A most interesting enzyme, known as hyaluronidase, has been extracted 

 from mammalian testes and from mammalian sperm. This substance is capable 

 of dispersing the follicle cells of the corona radiata present around most mam- 

 malian eggs when discharged from the ovary. (Sheep and opossum eggs as 

 well as those of the monotremes do not possess a layer of follicle cells around 

 the newly ovulated egg.) This dispersing effect aids fertilization, for it enables 

 sperm to reach the egg surface before degeneration processes occur in the 

 egg. Rowlands ('44) eff'ected artificial insemination in the rabbit with dilute 

 sperm solutions by adding the enzyme hyaluronidase from other sperm to the 

 dilute suspensions. Without the addition of hyaluronidase, fertilization did not 

 result. In certain cases in women where artificial insemination was tried but 



