Leech’s external and internal segmentation do not correspond to each other.
If the internal body is examined, it can be seen that the body is divided into 32 parts or segments which have their own corresponding brain.
Each of these segments possesses its own neuronal ganglia that are linked with the next.
It is the same single brain that exists in 32 segments throughout the body, anatomically.
Physiologically, as every ganglion regulates its corresponding segment and operates independently, it is said that physiologically it possess 32 brains.