DESCRIPTIONS OF GENERA AND SPECIES 321 



The worm was called ' niveus ' on account of its very white appearance ; it occurs 

 in earth which had been manured with fish de'bris, and was, on that account, and also 

 because of its look, mistaken at first for a Dipterous larva. No head-pore was found, 

 and, if present, it must be but small. The brain is deeply cleft behind, and the 

 two lobes formed by this furrow are slightly divergent, and have the appearance 

 of distinct lobes, owing to this fact and to the presence of a shallow lateral depression 

 at the side of the brain, just where they join the main mass ; there are two pairs 

 of muscles attached to the brain. The nephridia all have a short anteseptal part, 

 and the duct arises near to the septum. The dorsal vessel springs from the intestinal 

 sinus in the ninth segment ; it contains a cardiac body. The intestine is mainly 

 remarkable for the huge size of the peritoneal cells which clothe it. In the original 

 description of the .worm, MICHAELSEN mentioned as a character the absence of a lumen 

 in the whole of the alimentary tract lying behind the pharynx ; in the rectum 

 the lumen was wholly obliterated, while in the intestine the lumen was blocked 

 by stellate cells ; that this is not characteristic either of the genus or even of the 

 species, was subsequently shown by MICHAELSEN, who met with individuals living 

 in ordinary garden mould, whose alimentary tract was quite normal ; it is, therefore, 

 doubtless with justice, that MICHAELSEN attributed the peculiar condition of the 

 gut in the first studied specimens to the nature of their diet. It should be mentioned 

 that the specimens found in ordinary earth had been placed there by MICHAELSEN ; 

 after two years they showed the normal gut-structure. The reproductive organs 

 occupy the usual position. The funnels of the sperm-ducts are remarkable on 

 account of their small size. 



Genus PACHYDBILUS, CLAPAREDE. 



Syn. Lumbricus, 0. F. MULLER (in part.). 

 Clitellio, LUTKEN et alii (in part.). 

 Nais, O. F. MtiLLER (in part.). 

 Saenuris, HOFFMEISTER (in part.). 

 Enchytraeus, KATZEL et alii (in part.). 

 Archienchytraeus, EISEN (in part.). 

 Epitelphusa, DRAGO. 

 Lumbriculus, OERSTED. 



DEFINITION. Setae /-shaped. Head-pore between prostomium and buccal segment, 

 no dorsal pores. Brain incised behind ; nerve-chord often with outgrowths in 



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