Stuck can fairly be called a Symbolist when he wasn't painting portraits or genre scenes (I'm not aware of Stuck landscapes or still lifes, but there might be a few). His preferred subjects were nude or partly-clothed women, though he did paint some nude males, in more than one painting shown fighting over a nude woman.
His painting style varied considerably, but not in the form of moving from one style to another as time passed. That is, throughout his career we find fuzzy looking paintings along with crisp works and somewhat poster-like images. I presume Stuck established a set of painting styles during the first part of his career that he then deployed depending upon the subject of a work.
Two paintings from Stuck's 20s. Both completed the same year, but with different atmospheres. The murky style of Sphinx will reappear later, often with fuzzier brushwork.
Considerable contrast between the carefully rendered face and the rest of the painting.
Again, the greatest detail is in the faces, as might be expected. Otherwise, Stuck's anatomical work is still more true to reality than in some of the later paintings shown below.
I doubt that Stuck's clothing shown here were his usual painting togs ... but I just might be wrong.
Again, the contrast between carefully rendered parts and quite loosely done other areas.
By the 1910s Stuck added a style to his repertoire that had a flatter, more illustration-like quality.
His "Bathing Women" is sketchy across the board. Perhaps this was a study (though it's signed). Or maybe he was reacting to works by younger, post-1900, Modernist painters.
An example of his dark, fuzzy style. Only a few details are sharply depicted.
A poster-like painting. Flat, with some mural-style outlining along with some fuzziness for the women's bodies.
Presumably a commission, because most Stuck effects are absent.
A dark, somewhat fuzzy painting from near the end of his career.
What Stuck was doing near the end of his life. Not far from what he'd been painting for many years.