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Updated: May 10, 2025
That this animal had not strayed accidentally into the Lepas, but appertained to it as a regular and permanent guest, is evidenced by its considerable size in proportion to the narrow entrance of the test of the Lepas, by the complete absence of the iridescence which usually distinguishes the skin of free Annelides and especially of the Amphinomidae, by the formation and position of the inferior setae, etc.
The chief organs of motion are still the two anterior pairs of feet, which are slender and furnished with long setae; the third pair of feet loses its branches, and becomes converted into mandibles destitute of palpi. The labrum acquires a spine directed forward and of considerable size, which occurs in all the Zoeae of allied species.
The antennae cease to serve for locomotion, their place is taken by the thoracic feet, furnished with long setae, and by the long abdomen which just before was laboriously dragged along as a useless burden, but now, with its powerful muscles, jerks the animal through the water in a series of lively jumps.
The tail, of very variable form, always bears THREE pairs of setae at its hinder margin. The Zoeae of the Crabs usually maintain themselves in the water in such a manner that the dorsal spine stands upwards, the abdomen is bent forwards, the inner branch of the natatory feet is directed forwards, and the outer one outwards and upwards. Tails of the Zoeae of various Crabs. Pinnotheres. Sesarma.
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.
But what is most remarkable is, that they now appear under two different forms. The terminal setae of the second pair of antennae project between the cheliferous feet. Buccal region of the same from below; lambda, labrum. Head of the rarer form of the male, magnified 25 times. In the first place, and before inquiring into its significance, I will say a word upon this fact itself.
The five new pairs of feet are biramose, the inner branch short and simple, the outer one longer, annulated at the end, furnished with long setae, and kept, as in Mysis, in constant whirling motion. The heart acquires new fissures, and interior muscular trabeculae.
It is one of the spider crabs, or Oxyrhynchus, most of which have long horns projecting from the rostrum, and are more or less thickly covered with stiff curled setae, to which seaweeds, sponges, and other marine growths selected according to the taste of the bearer are attached.
Ultimately the leaves and spines fall away, the tubercles are levelled down, and the mature stem is regular and cylindrical, with tufts of white setae scattered over it. Flowers small, produced in spring; sepals 2 in. long, green, deciduous; petals small, dull purple, usually about eight in each flower. Fruit pear-shaped, 4 in. long; seeds very large, nearly ½ in. long and wide.
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