6 1 6 THE ANIMAL KINGDOM. 



According to Hatschek a longitudinal canal is formed in connection with 

 each cephalic kidney. Segmental nephridial funnels develope in each somite 

 in continuity with this canal, which then disappears, each nephridium 

 opening externally by its own pore. The young Polygordius has a pair of 

 eye-specks. 



Species of Protodrilus and Polygordius, Fraipont, Archives de Biologic, v. 1884, 

 note p. 250; the names as given by Fraipont have been followed here. 



Protodrilus Leuckarti, Hatschek, Arb. Zool. Inst. Wien, iii. 1880. P. pur- 

 pureus, Schneider, Archiv f. Anat. und Physiol. 1868, p. 56. P. flavocapitatus, 

 Uljanin, apud Hoyer, Z. W. Z. xxviii. 1877, p. 389; development of, Repiachoff, 

 Z. A. iv. 1881. P. Schneideri, Langerhans, Z. W. Z. xxxiv. 1880, p. 125. 



Polygordius lacteus, Schneider, loc. cit. supra. P. Villoti, Perrier, C. R. 80, 

 1875. Development, Hatschek, op. cit. supra, i. 1878; of head, Id. op. cit. vi. (i), 

 1885 ; Fewkes, Bull. Mus. Harvard, xi. (No. 9, 1883), p. 195 head-kidney, Fraipont, 

 op. cit. supra. 



Nervous system of Archi-annelida, Fraipont, op. cit. supra. This author is 

 stated to be preparing a monograph of the genus Polygordius for ' The Fauna and 

 Flora of the Gulf of Naples.' 



CLASS GEPHYREA. 



Vermes with a sub-cylindrical non-segmented body, usually brightly 

 coloured. The fore-part of the body is either invaginable, and provided ivith 

 tentacles, or prolonged into an extensile prostomium, which is readily cast off. 

 Setae may be present as an anterior ventral pair, and one or two posterior 

 circlets. The mouth is anterior, or at the base of the prostomium ; the amis 

 dorsal and anterior, or terminal and posterior. The nervous system consists 

 of a peripharyngeal band, with or without a supra-oesophageal swelling, and 

 of a ventral non-ganglionated cord. There are no specialised organs of res- 

 piration. A vascular system is usually present ; the coelome large. Specialised 

 corpuscles tinged with haemoglobin or haemerythrin are frequently found in the 

 coelomic fluid, and sometimes in the vascular. Nephridia are usually present. 

 The sexes are separate, the male sometimes degenerate ; and the genital pro- 

 ducts are either shed into the coelome and taken up by the nephridia ; or the 

 glands are continuous with their ducts. Exclusively marine and generally 

 distributed. 



Of the two sub-groups of Gephyrea, the G. achaeta and G. chaetifera, 

 the former contains the families Sipunculidae and Priapulidae, the latter 

 the Echiuridae. The Sipunculidae have the forepart of the body invaginable, 

 and this ' introvert,' often termed proboscis, is of considerable length, and 

 usually slender as compared with the rest of the body. The introvert is 

 generally covered with hooks, except in the genus Sipunculus 1 . There 



1 Billow found that the anterior part of the introvert was regenerated after removal in 3-5 

 weeks' time in Phascolosoma and Aspidosiphon (Biol. Centrablatt. iii. p. 14). Sipuncidus has often 



