And a few observations:
It seems to me that, actual blatant pornography aside, these images are pretty racy by Victorian standards. I've gathered a few photos for a future post which are actually supposed to be erotic, and they're surprisingly similar to these. Of course, the sexualisation of female singers/dancers/actresses is nothing new and is still going on merrily today, along with the sexualisation of just about everything else. But we have, thankfully, lost the idea of women on stage being somehow disreputable and the link with prostitution. Actually, I don't think we have lost it: I think it just slid, along with so much else, into the collective subconscious.
Another thing that struck me was how astonishingly healthy these girls look, in comparison with modern ballerinas. The third one perhaps excepted, these women display the female form in all its curvacous glory. They wouldn't last five minutes in modern ballet.