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The biramose maxillipedes appear to assist but slightly in locomotion. The forked tail reminds us rather of the forms occurring in the lower Crustacea, especially the Copepoda, than of the spatuliform caudal plate which characterises the Zoeae of Alpheus, Palaemon, Hippolyte, and other Prawns, of the Hermit Crabs, the Tatuira and the Porcellanae.
Xantho. It is further to be remarked that the Zoeae of the Crabs, as also of the Porcellanae, of the Tatuira and of the Shrimps and Prawns, are enveloped, on escaping from the egg, by a membrane veiling the spinous processes of the carapace, the setae of the feet, and the antennae, and that they cast this in a few hours.
Among the males of these various Bopyridae, that of Entoniscus Porcellanae occupies the lowest place; it is confined all its life to six pairs of feet, which are reduced to shapeless rounded lumps. The Amphipoda are distinguishable from the Isopoda at an early period in the egg by the different position of the embryo, the hinder extremity of which is bent downwards.
The caudal appendages sprout forth like other limbs freely on the ventral surface, whilst in other Prawns, the Porcellanae, etc., they are produced in the interior of the spatuliform caudal plate.
The pupae in both orders attach themselves by means of the adherent feet; those of the Cirripedes to rocks, shells, turtles, drift-wood, ships, etc., those of the Rhizocephala to the abdomen of Crabs, Porcellanae, and Hermit Crabs.
The long, spiniform processes on the carapace of the Zoeae of the Crabs and Porcellanae are not to be explained in this way, but their advantage to the larvae is evident. The formation of new limbs beneath the skin of the larvae is also to be referred to an earlier occurrence of processes which originally took place at a later period.
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