Alexandra’s “Princess Line”..

.. had a “sheath” or “cuirasse” bodice line that was even longer than the early ones.  It now had no waist seam and the bodice and skirt were cut in one – unlike any other garment previous which was always at least two pieces – bodice and skirt.

(Photos: left, 2-piece with cuirasse bodice or sheath bodice; right, the “new” Princess line of 1880 with bodice and skirt cut as one)