This is the part I'm not sure about. The alternate explanation I have goes like this:
- Snail A gets shocked a lot, as a result it gets really stressed out, altering its RNA/epigenetics to produce lots of stress hormones
- Lots of stress hormones lead Snail A to withdraw for a long time when touched
- Snail B gets an injection of Snail A's RNA
- As a result, Snail B starts producing lots of stress hormones
- Lots of stress hormones lead Snail B to withdraw for a long time when touched
This doesn't involve what we would typically regard as memory or learning, and certainly wouldn't generalize to a method of transferring memories in the general case. A modified experiment that I think would show genuine memory transferal would be to occasionally show red and green lights, have snails in group 1 shocked after the green lights only and snails in group 2 shocked after the red lights only, inject their respective RNA, and see if the receiving groups are distinguishable in their responses to red vs green lights.