492 CRUSTACEA MALACOSTRACA. 



freely locomotive, live on the juices of other animals, the mouth parts 

 being suctorial. The eyes are larger than in the adult and the mouth parts 

 are all present and styliform and the upper lip forms a half-tube. The second 

 thoracic legs, modified into a second pair of maxillipeds, lie parallel with 

 the mouth parts and are strongly hooked. From such larvae the two- 

 sexes emerge, after the last moult, in very different forms. In the male 

 (Anceus Risso, but Gnathia Leach has the priority) the head is very large 

 and bears powerful prehensile mandibles, like those of a beetle, on its 

 truncated front margin.* The maxillae have disappeared and the mouth 

 is a small orifice in the middle of the concave under side of the head. The 

 maxillipeds are broad, applied together as usual , and bear a setose 4-lobed 

 palp. The second thoracic feet are wide and valvular and the segment 

 to which they belong is small and closely united with the head, the 3rd 

 and 4th segments distinct, the 5th-7th wide and more or less completely 

 fused together. The 8th has disappeared. 



In the female (which has been described as a distinct genus under the 

 name Praniza Latr. ) the head is much smaller though the eyes are 

 larger than in the . male. The mandibles are absent, and the middle of 

 the body (4th-6th thoracic segments) is distended into a thin-walled 

 sack. The brood pouch is formed between the hypodermis of the under 

 part of the body and the cuticle which latter eventually splits segmentally 

 allowing the larvae to escape. The mode of fertilization of the eggs, and 

 of their entry into the brood pouch, have not been followed. 



It appears that in the adult state food is brought to the mouth in 

 currents, caused by the rhythmic movements of the maxillipeds. 



The genus Gnathia Leach is marine, and most species are littoral. 

 G. maxillaris Mont, in calcareous sponges ; British. G. Halidayi young 

 parasitic on fish, adults live independently in tubes (Delage). Euneognathia 

 Stebbing was obtained by the Challenger from a depth of 900 fthms. 

 in the X. Atlantic. 



Order 6. AMPHIPODA. f 



Malacostraca without a dorsal shield, with laterally compressed 

 body and gills on the thoracic feet and (except in the Laemodipoda) 



' Dohrn finds that these appendages are developed independently of 

 the mandibles of the larva, and hence refuses to recognize them as 

 mandibles. 



t C. Spence Bate, Catalogue of Amphipodous Crustacea in the British 

 Museum, London, 1862. E. van Beneden et Em. Bessels, Mem. s. la 

 form, du Blastoderme chez les Amphipodes, etc., Bruxelles, 1868. C. 

 Claus, Der Organismus der Phronimiden, Arb. Zool. Inst. Wien, T. 2, 

 1879. Delage, V. Contrib. a 1' etude de 1'appareil circutaloire des Crus- 

 taces edriophthalmes marina, Arch, de Zool. exp., ix, 1881. O. Nebeski, 

 Beitrage zur Kenntniss der Amphipoden der Adria, Arb. Zool. Inst. 

 Wien, T. 3, 1881. Paul Mayer, Fauna und Flora des Golfes von 

 Neapel, monog. VI. Caprelliden, Leipzig, 1882. Nachtrag, monog. 

 XVIII., 1890. Id., Die Caprellidae der Siboga-Expedition, Leiden, 1902. 

 C. Claus, Die Platysceliden, Wien, 1887. T. R. R. Stebbing, Challenger 

 Amphipoda, 1888. G. O. Sars, Hist. Nat. d. Crustaccs d'eau donee de 

 Norvege. Christiania, 1867, and An account of the Crustacea of Norway, 



