Who Is Pictured On This Stamp?

That's why I only watch Youtube TTS videos! You need a reliable source!

k

BTW, my initial reaction was Ernst Haeckel in his much later years, when he might have trimmed his beard down along the edges (as opposed to his normal wider bushy beard), but I couldn't find a portrait to match.

The problem is, in the late 19th and very early 20th Century, many of the male Western Scientists with beards all started to look alike as they got old! I guess it was a frat boy thing for older male scientists.