ISOPODA. 479' 



The eggs undergo their development in an incubatory pouch 

 formed by one (Tanais) or more pairs of oostegites developed 

 from the ventral thoracic region. The embryos are dorsally 

 flexed during their development, as in the Isopoda. The last 

 thoracic, and all but the last abdominal appendages are absent 

 in the newly hatched larva, as in the Cumacea. 



In Tanais dubius (?) Kroyer, from the coast of Brazil, according to 

 Fritz Miiller, the males resemble the females until the last moult. After 

 this they apparently cease to feed, the mouth appendages being lost, 

 and in respect of their secondary sexual characters appear under two' 

 forms. In one, which is more abundant, they bear some 12 to 17 olfac- 

 tory hairs on the anterior antennae, and have large and very mobile 

 chelae, for holding the female, while the others are provided with chelae 

 resembling those of the female, but are more richly equipped with 

 olfactory hairs. 



The Tanaidacea live on the bottom of the sea, in mud, fre- 

 quently in tubes formed of agglutinated particles, from shallow 

 water to a depth of over 1,000 fms. 



Fam. 1. Tanaidae. Tanais named by M. Edw. (subgenera Heterotanais r 

 Typhlotanais, Leptognathia, Tanaopsis, Cryptocope, Haplocope, Strongylura, 

 Anarthrura, Pseudotanais all G. O. Sars, Paratanais Dana) antennae 

 simple, mandibular palp absent, 2nd, 3rd and 4th legs nearly alike, and 

 the sixth abdominal leg short. 



Fam. 2. Apseudidae. Apseudes Leach, eyes sessile, anterior antennae 

 biramous, the posterior bearing an outer setose lobe, mandibular palp 

 present, 3rd thoracic leg large, the uropods elongated. Related genera, 

 Parapseudes G. O. Sars, and Sphyrapus Norman and Stebbing. 



Order 5. ISOPODA.* 



Malacostraca without a carapace and usually with broad and 

 somewhat flattened body, with seven free thoracic rings and with 



* H. Rathke, Untersuchungen iiber die Bildung und Entwickelung der 

 Wasserassel, Leipzig, 1832. Cornalia and Panceri, Osservazione Zool. 

 Anat. Sopra un nuovo genere de Crustacei laopodi sedentarii, Torino, 1858. 

 A. Dohrn, Die Embryonalentwickelung des Asellus aquaticus, Zeitschr. 

 fur wiss. Zool., Tom. xvii, 1867. N. Bobretzky, Zur Embryologie des 

 Oniscus murarius, Zeitschr. fur wiss. Zool., Tom. xxiv, 1874. R. Koss- 

 mann, Die Entonisciden, Mitth. Zool. Stat. Neapel, iii, 1882. R. Walz, 

 Ueber die Familie der Bopyriden, etc., Arb. aus dem Zool. Inst., etc., Wien, 

 T. 4, 1882. Schiodte, J. C. and Meinert Fr. Symbolae ad Monographiam 

 Cymothoarum, etc., Nat. Tidskrift., xii and xiii, 1879-83. F. E. 

 Beddard, Report on the Isopoda collected by H.M.S. Challenger, London, 

 1884-6. A. Giard et J. Bonnier Contrib. a 1' etude des Bopyriens, Trav. 

 de I'Inst. Zool. de Lille, T. 5, 1887. Id. Contrib. a 1' etude des Epicarides, 

 Bull. Scient. de la France et de la Belgique, 1895. J. Bonnier, Les Bopyridae. 

 Trav. Stat. Zool. Wimereux, T. viii, 1900. H. J. Hansen, Cirolanidae et 



