The Veliger's a lively tar, the liveliest afloat,
A whirling wheel on either side propels his little boat;
But when the danger signal warns his bustling submarine,
He stops the engine, shuts the port, and drops below unseen.
He's witnessed several changes in pelagic motor-craft;
The first he sailed was just a tub, with a tiny cabin aft.
An Archi-mollusk fashioned it, according to his kind -
He'd always stowed his gills and things in a mantle-sac behind.
Young Archi-mollusks went to sea with nothing but a velum -
A sort of autocycling hoop, instead of pram - to wheel 'em;
And, spinning round, they one by one acquired parental features,
A shell above, a foot below - the queerest little creatures.
But when by chance they brushed against their neighbours in the briny,
Coelenterates with stinging threads and Arthropods so spiny,
By one weak spot betrayed, alas, they fell an easy prey -
Their soft preoral lobes in front could not be tucked away!
Their feet, you see, amidships, next the cuddy-hole abaft,
Drew in at once, and left their heads exposed to every shaft.
So Archi-mollusks dwindled, and the race was sinking fast,
When by the merest accident salvation came at last.
A fleet of fry turned out one day, eventful in the sequel,
Whose head-and-foot retractors on the two sides were unequal:
Their starboard halliards fixed astern ran only to the head,
While those aport were set abeam and served the foot instead.
Predaceous foes, still drifting by in numbers unabated,
Were baffled now by tactics which their dining plans frustrated.
Their prey upon alarm collapsed, but promptly turned about,
With tender morsel safe within and the horny foot without!
This manoeuvre (vide Lamarck) speeded up with repetition,
Until the parts affected gained a rhythmical condition,
And torsion, needing now no more a stimulating stab,
Will take its predetermined course in a watchglass in the lab.
In this way, then, the Veliger, triumphantly askew,
Acquired his cabin for'ard, holding all his sailing crew--
A Trochosphere in armour cased, with a foot to work the hatch,
And double screws to drive ahead with smartness and dispatch.
But when the first new Veligers came home again to shore,
And settled down as Gastropods with mantle-sac afore,
The Archi-mollusk sought a cleft, his shame and grief to hide,
Crunched horribly his horny teeth, gave up the ghost, and died.