Vergil apparently never published the Ciris, for he re-used its lines, indeed whole blocks of its lines with a freedom that cannot be paralleled. The much discussed line of the fourth Eclogue:
Cara deum suboles, magnum Jovis incrementum,
is from the Ciris (I. 398), so is the familiar verse of Eclogue VIII (I. 41):
Ut vidi, ut perii, ut me malus abstulit error,
and Aeneid II. 405:
Ad caelum tendens ardentia lumina frustra,
and the strange spondaic unelided line (Aen. III. 74):
Nereidum matri et Neptuno Aegaeo,
and a score of others. The only reasonable explanation[3] of this strange fact is that the Ciris had not been circulated, that its lines were still at the poet’s disposal, and that he did not suppose the original would ever be published. The fact that the process of re-using began even in the Eclogues[4] shows that he had decided to reject the poem as early as 41 B.C. A reasonable explanation is near at hand. Messalla, to whom the poem was dedicated, joined his lot with that of Mark Antony and Egypt after the battle of Philippi, and for Antony Vergil had no love. The poem lay neglected till he lost interest in a style of work that was passing out of fashion. Finding a more congenial form in the pastoral he sacrificed the Ciris.
[Footnote 3: Drachmann, Hermes, 1908, p. 405.]
[Footnote 4: Especially in 8, 10, and 4. This method of re-working old lines reveals an extraordinary gift of memory in the poet, who so vividly retained in mind every line he had written that each might readily fall into the pattern of his new compositions without leaving a trace of the joining. Critics who have tried the task have been compelled to confess that the criterion of contextual appropriateness cannot alone determine whether or not these lines first occurred in the Ciris.]