(I have no idea whether this holds true in the novels. It has been decades since I read them.)
(Just to be thorough: as in all fiction, there are two other gender classifications in James’ stories: the pre-pubescent and the post-sexual. Children and the elderly sometimes play important roles in James’ work – “The Turn of the Screw” is a famous example. His story, “Crapy Cornelia”, is a touching account of a Mr.’s passage into post-sexuality.)
Compared to the number of Misses, there are an awful lot of Missuses in James’ stories. Most of them are widows, with an occasional divorcee. Their preponderance would baffle an actuary – a real one or a fictional one (a fictional actuary being one whose statistical base is the population of characters in literature).
The love object of a male James protagonist is usually a Mrs. When a Miss is the hero’s beloved and his objective, invariably, is marriage, he always has a Mrs. lurking in the background, an ex-lover or a partner in an ongoing sophisticated flirtation. More often than not, our hero seems to flee to his Mrs. simply in order to enjoy (or to allow the reader to enjoy) some adult conversation.
With one or two exceptions, the relationship between a James hero and his Mrs. is strictly platonic. Their intimacy is intellectual, not sexual, even if it was sexual in the past, before the story commenced. James’ Missuses are as coyly proper as is the Master, himself.
Just as James is what we would call extremely class-conscious (although he takes class so much for granted that it hardly seems conscious at all), and assumes that it is fortunate to be in one class and unfortunate to be in another, and never the twain shall meet, he is acutely aware (to the point of taking it for granted) of a similar barrier between virgin females and everyone else, and is quite clear as to which group (“everyone else,” of course) it is fortunate to belong.
In the 42nd story I read, “Patagonia”, I was gratified when James explicitly affirmed my three-gender theory.
[I] dozed a great deal, lying on my rug with a French novel, and when I opened my eyes I generally saw Jasper Nettlepoint passing with his mother’s protégée on his arm. Somehow at these moments, between sleeping and waking, I had an inconsequent sense that they were a part of the French novel. Perhaps this was because I had fallen into the trick, at the start, of regarding Grace Mavis almost as a married woman, which, as every one knows, is the necessary status of the heroine of such a work.
As proof of the impossibility, in James’ view, of a female character’s gender being something other than Miss or Mrs., or falling between them, or being both at once, (spoiler alert) Grace Mavis’s fate is that of anyone (at least according to the theories of Emil Durkheim) whose social status has become impossibly ambiguous. James’ harsh adherence to a propriety in which only Misses or Missuses are allowed, ruins what could have been a delicious classic shipboard comedy.
Although other stories of James’ are more risqué, more like the French novels that James’ characters like to indulge in or denounce, “Patagonia” does include one of James’ boldest references to unmarried sex.
Of course it was not impossible that [Jasper Nettlepoint] might be inclined, that he might take it (or already have taken it) into his head to marry Miss Mavis; but to believe this I should require still more proof than his always being with her. He wanted at most to marry her for the voyage.