{{explanation}}
3s & 4s start on opposite sides

1-8
: 1s+2s also 3s+4s dance Double Figs 8 (1s & 3s cross down, 2s & 4s dance
  up). All finish in middle, 2H joined with partner, ready for ...
9-16
: 1s+2s also 3s+4s dance Poussette. 2s & 3s end on sides, 1s & 4s BtoB
  with partner ready for Double Triangles.  2 1 (4) (3)
17-24
: All dance Double Triangles with 1s+4s joining nearer hands in middle and
  other hand with nearest corner. On last bar 1s & 4s rotate extra 1/4
  round to end RSh to RSh in middle (1M & 4W facing up, 1L & 4M facing
  down)
25-28
: 1M followed by 4L also 4M followed by 1L dance out through ends & cast
  to right to end 2 4 (1) (3)
29-32
: 4s+1s dance RH across. End near hands joined with partner facing down
33-40
: Mirror reels of 4 on sides (2s & 1s dance down, 4s & 3s cast out/up to
  start). End 2 4 (1) (3) ready to flow into Double Figs 8