That it is the most complete is at once evident. That it is the
truest must be assumed, in the first place, because the mode of life of
the various ages is less different than in the majority of the other
Podophthalma; for from the Nauplius to the young Prawn they were found
swimming freely in the sea, whilst Crabs, Porcellanae, the Tatuira,
Squilla, and many Macrura, when adult usually reside under stones, in
the clefts of rocks, holes in the earth, subterranean galleries, sand,
etc., not to mention other deviations in habits such as are presented by
the Hermit Crabs, Pinnotheres, etc.,--and secondly and especially
because the peculiarities which distinguish the Zoea of this species
particularly from other Zoeae (the employment of the anterior limbs for
swimming, the furcate tail, the simple heart, the deficiency of the
paired eyes and abdomen at first, etc.) are neither to be deduced from a
retro-transfer of late-acquired advantages to this early period of life,
nor to be regarded at all as advantages over other Zoeae which the larva
might have acquired in the struggle for existence.
A similar development must have been once passed through by the
primitive ancestor of all Malacostraca, probably differing from that of
our Prawn, especially in the circumstance that it would go on more
uniformly without the sudden change of form and mode of locomotion
produced in the latter by the simultaneous sprouting forth and entering
into action in the Nauplius of four and in the Zoea of five pairs of
limbs.
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