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Updated: May 5, 2025
The accompanying representation of the embryo of Squilla shows that it possesses a long, segmented abdomen without appendages, a bilobate tail, six pairs of limbs, and a short heart; the latter only pulsates weakly and slowly. If it acquires more limbs before exclusion, the youngest larva must stand on the same level as the youngest larva of Euphausia observed by Claus.
To this we may answer that the occurrence of the Zoea-form in all the above-mentioned Decapoda, its existence in Peneus during the whole of that period of life which is richest in progress and in which the wide gap between the Nauplius and the Decapod is filled up, its recurrence even in the development of the Stomapoda, the occurrence of a larval form closely approaching the youngest Zoea of Peneus in the Schizopod genus Euphausia, and the reminiscence of the structure of Zoea, which even the adult Tanais has preserved in its mode of respiration, all indicate Zoea as one of those steps in development which persisted as a permanent form throughout a long period of repose, perhaps through a whole series of geological formations, and thus has also made a deeper impression upon the development of its descendants, and formed a firmer nucleus in the midst of other and more readily effaced young states.
The youngest larva of the Schizopod genus Euphausia observed by Claus, stands very near the youngest Zoea of our Prawns; but whilst its anterior antennae are already biramose, and it therefore appears to be more advanced, it still wants the middle maxillipedes. In it also Claus found the heart furnished with only a single pair of fissures.
Saw a young Emperor this morning, and whilst trying to capture it one of Wilson's new whales with the sabre dorsal fin rose close to the ship. I estimated this fin to be 4 feet high. It is pretty to see the snow petrel and Antarctic petrel diving on to the upturned and flooded floes. The wash of water sweeps the Euphausia across such submerged ice.
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