. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. 472 CRUSTACEA. of the second pair are by far the largest; they are moved more or less outwards and are pi'ovided with a very large chela. The three following pairs resemble each other in size and structure, each ending in a smaller rounded chela. Accordingly there remain for locomotion only the three pairs of legs of the last three uncovered thoracic segments; they have the form of biramous swimming feet. The abdominal swimming feet, however, are much more developed and bear the branchial tufts on t
. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. 472 CRUSTACEA. of the second pair are by far the largest; they are moved more or less outwards and are pi'ovided with a very large chela. The three following pairs resemble each other in size and structure, each ending in a smaller rounded chela. Accordingly there remain for locomotion only the three pairs of legs of the last three uncovered thoracic segments; they have the form of biramous swimming feet. The abdominal swimming feet, however, are much more developed and bear the branchial tufts on their external lamella?. The two sexes are only slightly different. The male is, however, easily to be recognised by the possession of the pair of rods at the base of the last pair of thoracic feet, and also by the slightly modified form of the first pair of abdominal feet. Me tarn orphosis.—The post - embryonic development consists of a complicated metamorphosis, which, unfor- tunately, is as yet not com- pletely known to us. The youngest larva} observed (about 2 mm. long) already possess all the segments of the tho- rax ; but the abdomen, except the caudal plate, is still un- developed. They are thus very different from the Zoaea of the Decapoda. Later larval stages are described as Alima and Erichthus (fig. 370). The Stomato2)oda are found exclusively in the warmer seas. They are excellent swimmers and live by preying on other marine animals. Fam. Squillidae. SqnUla mantu Eond., Sq. Desmarestii Eisso, Adriatic and Mediterranean. (3) Sub-order: Schizopoda.* SttuiU Thoracostraca with large, usually soft ceplialo-thoracic shield and eight pairs of biramous thoracic feet, which are similarly formed and frequently hear freely-projecting gills. * G. O. Sars, " Hist. nat. des Crustac^s d'eau douce de Norv^ge," Chrisliania. Fig. 370.—Young AUma larva. Af. Abrlominal feet (pleopods); Mxf, anterior maxillipeds ; Mxf, the large maxillipeds (second pair).. Please note that
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanimals, bookyear1892
