What animals do not have heads?

That's a tricky question! It depends on how you define "head".

* Technically, all animals have a front end: Even organisms like sponges, which lack clear body parts, have a direction they face.

* Animals with radial symmetry: Like jellyfish and starfish, have a central point but no clear head. They can face in any direction.

* Animals with bilateral symmetry: Like humans and dogs, have a head at the front end.

So, the answer is that no animals are entirely without a front end or head in the biological sense.