The two plants in the photo were volunteers probably from compost I used to amend my raised bed soil. The plant on the right produced the usual acorn squash. The one on the left however developed these two white gourds early. They haven't changed color for two months. Are these a color variant of acorn squash or another species?

Moved to Vegetables and Fruit forum.

Yes there are several varieties of white acorn. Cream of the Crop is probably the best known. But squash cross breed easily among the species so most likely you have a mutt. White scallop could be in the parentage among others. Only careful and deliberate seed savers can get true squash seeds.

Thanks, farmerdill. A careful seed saver I am not, but I do deliberately harvest some.

Jumpster, it's hard for me to tell from the photo, but do they look like tiny pumpkins? I grow a variety called "Baby Boo" that looks like a very small white pumpkin; I use it for fall decorating.

Weedwhacker, Pumpkins can't be ruled out I suppose, but chances seeds got disseminated into the bed is very slim. Closer photo attacked. New flowers still forming, so I will see what develops.

Well, they certainly look like Baby Boo to me, but of course there are so many varieties of squash and pumpkins, along with random crossing, that it would be impossible to say for sure. Mine do seem to grow in pairs like that.

Here's a photo of Baby Boo from the database:

Of course, the term pumpkin is just a lay term for a Cucurbita thing with a certain shape.
As Dillard says, cucurbita has a couple cultivated species that make up all the things we call squash, pumpkins, (and some gourds even?) and mixing happens. So something mixed, made seed, that got in your garden via compost or some way, and voila- white mini pumpkins

Sallyg, Glad to have examples of what sparked Darwin's and Mendel's curiosity in my yard.