DESCRIPTIONS OF GENERA AND SPECIES 323 



seem to be only explicable on the theory that the worm is a Pachydrilus. Deago 

 certainly speaks of the setae as 'quasi diritte e corte'; but later says: 'Setole 

 alquanto ricurve alle estremitk.' Construing the word ' quasi ' rather freely will, 

 without any great effort, bring the genus Epitelphusa within the genus Pachydrilus. 



The chief characters of the genus are given in the definition; a few of these 

 characters, and some others, may now be stated more in detail. 



One of the most characteristic structural features of the genus, though confined 

 to a few species, is the outgrowths of the ventral nerve-chord in certain segments ; 

 these occur in P. lineatus, P. inaximus, P. nervosus, and P. pagenstecheri ; they 

 were first described by Eisen (13). 



EisEN does not do much more than briefly refer to these structures and figure 

 them in P. nervosus; he remarks (p. ^^), 'In Archienchytraeus nervosus the ganglionic 

 swellings of the fourth and the eleventh and twelfth segments attain an enormous 

 development, and surpass the supra-oesophageal ganglion several times in size. It 

 is remarkable that the said swellings are found only in the segments containing 

 the organs of generation. In A. profugus and nasutus I have sometimes found 

 certain irregular nervous enlargements in some of the segments, but not to be 

 compared in size with those above.' 



The structures ai-e figured (not in section) on Plate viii, fig. i6 c and d. Miohaelsen 

 recorded some years after a similar structure in P- *■ germanicus'( = P. lineatus); in the 

 segments following the clitellum are lateral wing-shaped outgrowths of the nerve- 

 chord, consisting of ganglion-cells ; they are compared to somewhat similar structures 

 found by Timm in Phreoryctes; in his paper upon the Oligochaeta of South Georgia 

 (15, p. SS)' MiCHAELSEN states that similar structures exist in P. maximus. 

 In this paper these outgrowths are described in all of the three species in which 

 they were then known to occur; they show constant, though small, difi'erences in 

 these three species, agreeing in their main characters in all three. They are formed 

 as a proliferation of the ventral mass of cells of the nerve-chord ; in P. nervosus 

 this mass is lobate, and projects freely into the peritoneal cavity on either side 

 of the nerve-chord, and independently of it. In the two other species they are 

 in contact with the nerve-chord everywhere; in P. lineatus they approach each 

 other dorsally. 



In the region where these structm-es exist, the nerve- chord sends a single 

 median nerve to the body-wall, which is accompanied by a branch from each 

 of the lateral masses; arrived at the epidermis, the mass of nerve-fibres spreads 

 out right and left, and the epidermis is here modified, the cells being long and 

 spindle-shaped, without any admixture of gland-cells. This region of the epidermis 



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