Thy two breasts are like two young roes - I have met with many attempts to support this similitude, or rather to show that there is a similitude; but I judge them unworthy of citation. The poet speaks the language of nature; and in a case of this kind, where the impassioned lover attempts to describe the different perfections of his bride, language often fails him, and his comparisons and similitudes are often without strict correctness. In love songs we have heard ladies' necks compared to that of the swan, not only for its whiteness, but also for its length! The description here shows more of nature than of art, which I consider a high recommendation.
Feed among the lilies - It may be the nipples especially, which the poet compares to the two young roes; and the lilies may refer to the whiteness of the breasts themselves.