CONTRIBUTIONS TO THE ANATOMY OF THE HIRUDINEA. 489 



the cells of the "apical lobe;" the lumen here passes through 

 the '' apical lobe " to ^ as a network without receiving any- 

 collecting ductules, and at^, which may be termed the "apex/' 

 the lumen becomes single, and from that point to where it 

 enters the vesicle simply perforates a series of drain-pipe cells 

 (fig. 48, d, woodcut, fig. 7). 



The duct in this condition — i. e. Avith its own special walls — 

 passes back through the " apical lobe " lying between the other 

 cells (woodcut, fig. 7), through in the same manner the portion 

 f — e, through the " main lobe '' from e to A, where it emerges 

 to penetrate the " apical lobe " once more, and, passing back 

 past/, enters the end of the " main lobe " at d. It now traverses 

 the main lobe to h, where it emerges again to pass to the vesicle 

 {j), being in its whole course from the funnel up to^ an intra- 

 cellular duct. In my previous paper I described a portion as 

 a "central duct" — an intercellular portion lying between the 

 cells in the lobes which it traverses — but the discovery^ of the 

 nucleated protoplasmic walls (fig. 48) of this portion of the duct — 

 in other words the discovery, that it was an intracellular and not 

 an intercellular duct — necessitates the abandonment of the term, 

 and results in the description given above. The other new point 

 respecting the passing of the network of lumina into the single 

 lumen at g, 1 saw something of before, although I had not 

 fully understood it.^ The vesicle and the duct from the vesicle 

 to the exterior {k — /) need no further description. The lumen 

 of this region is surrounded by numerous ciliated cells. 



Aulostoma. 

 The funnel is quite similar, and similarly placed, to the funnel 

 in Hirudo; its existence has also been always heretofore 

 denied. The structure of the remainder of the nephridium also 

 closely resembles the structure found in Hirudo. It has been 

 fully worked out by Schultze, and his results agree with my 



' A. G. Bourne, ' Quart. Journ. Micr. Sci.,' vol. xxii, 1882, p. 337, " The 

 'Central Duct' of the Leech's Nephridium." 



2 A. G. Bourne, 'Quart. Journ. Micr. Sci.,' vol xx, 1880, PI. XXIV, 

 fig. 2, X. 



