A Singular Reason

Stern his cause
Race of creation
Life a season
High tubes ascent
Morning light's arrest
Silently he perpetrates
Beginning masculine haste
Split second timing
Always fine tuning
Head now aligned
Singular he's alone
Entering her womb
Excited tussles reach
An entrance grand
For feminine breach
His lady serving
One well prescribed
With copious release
Fertile at ease
Make way for--
The sperm please!