The professor had his qualms about this picture.
He was sure that the face was "Too waxy looking" (See detail, right)

In the professor's own words:

"How'd you like that, you old bag? I told you what I was going to do if you didn't stop nagging me, but NO - you have to go right on like I was a child of three! Nag, Nag, Nag. Christ alone knows how many times I've heard that I'll never amount to much - well, we'll see how you like not amounting to much, you mutton-faced slag! God Almighty - I paint my bloody fingers to the bone, and what do I get? I get “What's that supposed to be? Looks like a squashed Beetle, that does” don't I? You've never liked me. You've never said one encouraging word to me in your bitter old life. You criticize every bloody thing I do. Well, the Hell with you - you dried up old bitch!"