Theme with Variations

I never loved a dear Gazelle--
Nor anything that cost me much:
High prices profit those who sell,
But why should I be fond of such?
To glad me with his soft black eye
My son comes trotting home from school;
He's had a fight but can't tell why--
He always was a little fool!
But, when he came to know me well,
He kicked me out, her testy Sire:
And when I stained my hair, that Belle
Might note the change and this admire
And love me, it was sure to dye
A muddy green, or staring blue:
Whilst one might trace, with half an eye,
The still triumphant carrot through