Bonnard met Marthe in 1893 when she was 24. They married and remained together until her death. She became not only his wife but his model. She had a fondness for the bath and some of Bonnard's best works are the Baignoires. Nude in Front of the Mantlepiece is one example.
There is a parallel to Max's wife who, 'when she fell ill, took to extended baths in the afteroon' (p 153).
The house is on Avenue Victoria.
The word homunculus comes from the Latin for 'little human'. It used to be believed that the sperm or egg contained a tiny 'preformed' human being. Generally, homunculi were seen as tiny figures grotesquely possessed of adult human features.