Sounds fun, doesn’t it? Unfortunately, I wasn’t the one doing the growing.
The flatworms were the ones growing the brains/heads. Scientists somehow induced them using electricity to grow the brains of another flatworm species. It’s really complicated sciencey stuff, so I’m not sure how they did it exactly, but it worked. The flatworm suffered no known consequences, other than the facts that the shape of the subject’s head changed and, obviously, he had the brain of a different species of worm.
The shape change was only temporary, because flatworms naturally regenerate. Unlike earthworms, if you cut almost any flatworm of the planarian genus in half in any way, it will grow back into two worms. If you cut it into six pieces, you’d have six new worms, etc.. Therefore, the experimental worm eventually grew back his old head and brain, without any damage done.
If you’re wondering why the biologists at Tufts University are growing flatworm brains, it’s because they’re hoping they can use their research and data to help with human problems like birth defects. They are also hoping that they can make humans regenerate body parts after sustaining an injury.
This is one reason I do like school, however tiring it can be. Learning stuff like this is very fun!