"Fertile eggs" refer to eggs that have the potential to develop into baby chicks or other animals if they are fertilized by a male's sperm. Full definition
The adult female worm produces fertile eggs that are passed in the infected cat's feces; the eggs need several days to several weeks to develop in the larvae stage. (yourpetspace.info)
It not only kills adult fleas but it stops them from laying fertile eggs, and it kills off all larvae and eggs at the same time too. (tatochip.com)
As the segments mature, they each make fertile eggs, which are stored in packets of sixty to one hundred eggs. (safarivet.com)