SPERM AND EGG GAMONES 45 



inactive and swim slowly. Small amounts of an extract of eggs will cause 

 them to swim vigorously. Gynogamone II agglutinates sperm. The sperm 

 surface becomes very sticky and the sperm will stick together by their heads, 

 thus forming clumps (Fig. 20). The surface of the sperm is rendered 

 adhesive, and this property may cause the sperm to adhere to the surface of 

 the egg. 



Extracts from the sperm give at least two androgamones, I and II. 

 Androgamone I paralyzes sperm movements. This substance is apparently 

 responsible for the fact that sperm as they are first shed are almost motion- 

 less. Such a static condition is of great value because the sperm cell is very 

 small and has no energy reserve in the form of food. If it is swimming 

 actively it uses up the small amount of energy it has and dies rapidly. If the 

 swimming of the sperm is prevented, the sperm life is prolonged many times. 



Androgamone II dissolves the outer layers of the egg and makes the 

 surface of the egg accessible to sperm. Most eggs have some kind of outer 

 coating outside the cell membrane. In the sea urchin egg which we are now 

 discussing there is a jelly surrounding the egg. If eggs are placed in an 

 extract containing androgamone II, the jelly completely dissolves (Fig. 20). 

 Thus androgamone II is sometimes called a lysin because it dissolves the 

 jelly, and in some sperm it is identified with a hyaluronidase — an enzyme 

 which breaks down jellies, causing them to liquefy. Mammalian sperm con- 

 tain hyaluronidase, which plays a role in fertilization. In rabbits, the use of a 

 low concentration of sperm for artificial insemination results in a failure of 

 fertilization. If a sperm extract containing hyaluronidase is added to this low 

 concentration of sperm, fertilization is successful. 



The actions of these substances can be linked in such a way as to give a 

 very plausible explanation of the events leading to fertilization in the sea 

 urchin egg. The sperm as discharged contain androgamone I, which inhibits 

 their motility, thereby prolonging their life. When, however, they come 

 under the influence of gynogamone I from the egg, the sperm are activated 

 and begin to swim. When the sperm get into the surface of the jelly then 

 androgamone II, the lysin, dissolves the jelly so that the sperm get to the 

 surface of the egg itself. When they get to the surface of the egg, gynogamone 

 II from the egg changes the surface of the sperm, rendering it adhesive so 

 that the sperm stick to the surface of the egg. In addition, there appears to 

 be in some eggs a substance which has a directive effect on the swimming 

 movements of sperm so that sperm are "attracted" to the surface of the egg. 



