Diffusible factors in anuran fertilization.

Anuran eggs are shed surrounded by a jelly material which is deposited by the oviduct as they descend through it. As soon as they come in contact with water, some components are released from the jelly coats into the inseminating inedium. The present review summarizes the information bearing on the problem of these diffusible factor involvement in fertilization. Evidence exists indicating that they are likely to exert some specific as well as protective influence on the spermatozoon. Their activity is discussed in connection to the acrosome reaction and the role of the jelly in the fertilization process. Attention is also drawn to some adaptive features of anuran fetrillization, suggesting that they would represent a transitional form between typically external and internal fertilization.