Melons (muskmelons,honeydews, etc.) and watermelons are two different species and will not cross-pollinate with each other. But, the various varieties of melons will cross-pollinate with each other just as different varieties of watermelon will cross-pollinate with each other. So, if you plan on saving seeds for replanting make sure that you plant different varieties far enough apart to ensure their pollen does not get into each others plants!!!
Choose large, well-formed fruits with good color and flavor from vigorous, disease-free vines. Doing so with watermelon is easy as the seeds are mature when the fruit is harvested when they are fully mature for fresh eating. Muskmelons are often harvested before they are fully ripe therefore you will want to let the fruit age about 3 weeks to ensure the seeds are fully mature and ready for saving. You will not want to eat these fruits!
Scoop out the seeds from the melon cavity with a spoon. With watermelons you can dig (pop) out the seeds from the flesh with a spoon, fork or by using your tongue/teeth and spitting them out.
Some sources say that the seeds do not need to be fermented, but just washed well with water and spread out to dry. Other sources says to let the seeds sit in water for a couple of days to help in separating the seeds from the flesh and to kill the bacteria that may cause problems in the future crop. If you choose to let them soak, make sure to wash them well after the soaking period.
Spread the seeds on paper toweling for a couple of weeks in a warm place to dry. Test for dryness by snapping a seed or two in half. If they snap in half went bent, they are dry enough to save.
Keep your fork