What is actually meant by "parallel paths" in a simplex progressive lap winding of a DC Generator?
Since the ends of each winding are bend inwards ( the beginning of a winding is placed at one lamella and the end of the same winding is placed at the next adjacent lamella this type of winding is called lap winding.
If you follow the windings you will find two parallel branches of windings for a 2 pole dc generator. For a four pole generator you will find 4 parallel branches of windings. From brush to brush you can consider each winding as a dc source and they are all in series so you will find Brush (lamella)- winding- lammela - winding -lammela - winding - brusch (lamella). This in two paths for a 2 pole machine and 4 paths for a 4 pole machine and so on.
Explanation of a wave winding and more in depth information you can find in
http://www.electrical4u.com/armature-winding-pole-pitch-coil-span-commutator-pitch/