Walter Garstang (9 February 1868 - 23 February 1949), a Fellow of Lincoln College, Oxford, and Professor of Zoology at the University of Leeds, was one of the first scientists to extensively investigate  the developmental biology of marine invertebrates. His best-known works on this topic were his poems published as Larval Forms and Other Zoological Verses, which describe the life histories of several marine species, as well as illustrating some controversies in evolutionary biology of the time.

The trochophores are larval tops the polychaetes set spinning, with just a ciliated ring, at least in the beginning.

They feed, and feel an urgent need to grow more like their mothers, so sprout some segments on behind, first one, and then the others.

And since more weight demands more power, each segment has to bring, its contribution in an extra locomotive ring.

With these the larva swims with ease, and, adding segments more, becomes a polytrochula, instead of trochophore.

Then setose bundles sprout and grow, and the sequel can’t be hid.

The larva fails to pull its weight, and sinks,

an Annelid.