It was an experiment with seaweed.
4 seconds sound clip from the Bride of Frankenstein movie soundboard.
You can hear this line at 00:23:51 in the Blu-ray version of the movie.
Quote context
[...]
- Poor archbishop. He has his hands full.
- There. That will keep you quiet.
- My next is very conventional, I'm afraid, but you can never tell how these things will turn out.
- It was an experiment with seaweed.
- Normal size has been my difficulty. You did achieve size. I need to work that out with you.
- But this isn't science. It's more like black magic.
- You think I'm mad. Perhaps I am.
- I grew my creatures, like cultures, grew them as nature does, from seed.
[...]