I wish I could take credit for a good answer, but I used Google and found this link:
For a very quick explanation, here is a quote from the page:
“In general, a scientific law is the description of an observed phenomenon. It doesn’t explain why the phenomenon exists or what causes it. The explanation of the phenomenon is called a scientific theory. It is a misconception that theories turn into laws with enough research.”
For these reasons, we still have things like “Germ Theory” and “Cell Theory” (and “Evolutionary Theory”, of course) that will not eventually morph into Laws, given enough time.