This variation is an excellent challenge, testing rhythmic precision and clarity of articulation. The off-beat up-bow A slow to moderate speed bouncing stroke. can start on or off the string (although in bar 18 Ševčík indicates that you should lift the 1st down bow and start the 2nd quaver from the air). Practice to begin with at half tempo, starting from the string to make sure that your up-bow spiccato movement is regular and reliable.
The action of hand and fingers (A short quick action that requires a clear connection and then leaving of the string so that the note will ring on after the bow leaves the string.) is supported by a passive reaction in the upper arm. Practice this stroke on open strings to begin with. After each up bow the hand needs to reform and regain its neutral shape so that it can activate the next up bow.
Develop the musical line by following the melodic contours and observe the different character of the intervals (e.g. in bar 2 the minor 6th on the first two beats is musically stronger than the minor 3rd on beats 3 and 4).
The A fast bowstroke where the hair stays in contact with the string while the stick bounces. bowing in bar 3 represents a challenge since it starts on an up bow and it may help to activate the first up bow with a strong impulse from the forearm.