There’s no rule that regulates how animals obtain the necessary genetic material to reproduce.
1. BANANA SLUGS MATE USING PENISES ON THEIR HEADS
Banana slugs are huge, they eat your garden, and they leave a slimy trail as they squirm across the ground. Their method of reproduction is no more pleasant than their appearance: The scientific name for one species of banana slug is Ariolimax dolichophallus, the second part of which means “long penis,” and it’s apt.