[Edit, 1/14/2013: Newcomers, you may want to see my tag for the polonaise, which will show you all of the Galerie des Modes polonaise plates I've translated so far. There are more plates than I give below, plus they have longer descriptions that I've also translated. I very definitely stand by my "no waist seam" pronouncement at this time.]
"Polonaise de toile bleue et blanche..." Galerie des Modes, 1779; MFA 44.1390Polonaise de toile bleue et blanche vermicelée garnie à plat de bandes de toile peinte de toutes couleurs sur fond blanc.
Polonaise of vermicelée blue and white linen, trimmed with flat bands of multicolored painted linen on a white ground.
The dress shown in this fashion plate, labeled "Polonaiʃe de toile bleue et blanche vermicelée ..." has much more of the skirt pulled up than the extant gown linked above. The skirt of the extant gown is clearly a normal, full-length skirt that has been drawn up into folds, but the skirt in the fashion plate appears to have been specially-cut in order to be able to form the three rounded "petals". It's possible that this could be artistic license, but we also have this dress: MMA 1982.32.
It's difficult to tell from a photograph, but the skirt of this polonaise seems to have been treated differently than that of the rucked-up anglaise. The hem may have been cut partially into the petal shapes, or perhaps the difference is in the way it has been pulled up. There is also a difference in the bodice: the anglaise uses several shaped pieces to form the back, but the polonaise uses three back seams, as in a man's coat. It also does not have a waist seam. The existence of polonaise caracos without drawn-up skirts seems to indicate that the cut of the back was just as important as the skirts.
(A large selection of polonaises can be found in my Pinterest account.)
"Polonoise vue par derriere ..." Galerie des Modes, 1780; MFA 44.1494
Polonoise vue par derriere, elle est de taffetas garnie de gaze. Sa coeffure est un bonnet moyen avec une barbe de gaze toute simple.
Polonaise seen from the back, it is taffeta trimmed with gauze. Her headdress is a medium cap with a simple gauze lappet.
There are a few commonalities between the gowns labeled "polonaise" in the fashion plates. It seems most common for polonaises and their (short) petticoats to be made to match. The front corners of the skirt were cut with a curve, so that the skirt swept back over the petticoat smoothly, and the skirt was trimmed all around with a ruffle or a stripe of different-colored fabric. The fashion plates also show women walking in the country, implying that the proper setting for these gowns is in informal situations. Most of these have a ruched gauze cuff at the elbow, which may also be part of the style. Though many were worn completely closed at the center front from about 1778, the polonaises that were left open in the front were worn over a "peaked high stomacher".
What the fitted gowns with skirts tied up with rings and tapes were called is somewhat mysterious. A French fashion plate depicting this can be seen here; the artist or caption-writer used the adjective "rétroussée" ("tied up", "tucked up", ) to describe what they specifically identify as an anglaise. Thus far, I've been unable to find the phrases "skirts à la polonaise" or "polonaised skirts" at all during the period. However, in the poem "The Ladies Head-Dress", quoted in The Cut of Women's Clothes and The Quaker, "Chloe" is described as having "her gown be tuck'd up to the hip on each side". It seems most likely that the French and the English both described the style with ordinary language, rather than adapting the term "polonaise" - which makes sense, as their polonaise gown was identified more by the cut than by the draping.