The undercarriage retracts with the top of the leg moving aft and the diagonal struts pull the wheel vertical until the wheel has moved just over half-way into the nacelle, facilitating wheels-up landings with minimal damage.

Hi Bob,
Many thanks for your interesting comments on my query.You've certainly done a great deal of research into this aircraft.Little-known aircraft of the 1930s interest me a great deal though it can be frustrating trying to find information about them,all part of the fun I suppose.
Thanks again and Happy New Year!
Brian.

Brian,
Yes, the photographer has gone to a great deal of trouble to position those airmen to cause maximum confusion 70 years later! However, if you look at the chap on the right, you can see that he hasn't done his job properly, there is what looks like an open wheel-well in the engine nacelle behind him indicating, if my interpretation is correct, that the undercarriage was retractable.
The P.W.S. 33 has a page in Wikipedia. The photograph there has no airmen (photographs; for the obscuring of) in it, and you can see the undercarriage quite clearly, it looks very much like a retractable type, with 'H' type oleo legs and struts. However, there are no undercarriage doors visible.
The Polish firm Ardpol make a 1/72 scale model of the PWS33 and there is a photo of the parts and of an assembled model on their web-site. Again, there are wheel well cut-outs in the nacelles, but no undercarriage doors.
What is needed is an air to air photo; the nearest thing I could find was the box-art of the Ardpol model, a fine illustration, except it is a three-quarter view from above and the wing neatly hides the area under the nacelles.
So, the final verdict seems to be probably retractable, but not quite certain.
Bob

The PWS 33 advanced trainer is very similar in appearance to the British Reid&Sigrist RS1 Snargasher twin-engined,three seat advanced trainer prototype first flown in early 1939.It did not go into production though its performance and handling was reported to be good in both normal and aerobatic flight when it was tested at the Martlesham Heath Test Establishment.The British aircraft had a fixed undercarriage.Did the PWS 33 have a retractable undercarriage?In the photograph the three Polish Air Force airmen are standing in front of the main wheels and it is impossible to see if the undercarriage is a fixed or retractable type.

The plane was built as a trainer for polish multirole twin engine fighter PZL P.38 Wilk (Wolf) When the P.38 project was screpped the P.W.S. 33 was not needed anymore.
Also the plane was named Wyżeł (pointer)