400 



HIRUDINEA 



their simplest form in such a type as Glossiphonia the Khyn- 

 ehobdellae, to which this genus belongs, being indeed in most 

 particulars less specialised than the G-nathobdellae. Her< 

 we have a distinct funnel opening freely into the median < 

 ventral coelomic space, which is immediately followed by 

 rounded swelling termed by Oka x the capsule ; this is filled 

 with cells, in the interstices of which the ductules are situated 

 and meander. There is in this capsule a very strong likeness t( 

 the glandular brownish swelling which immediately follows tin 

 funnel in the nephridia of certain of the aquatic Oligochaeta, foi 

 example the Naids, where, as Vejdovsky has shown, there is 

 similar " rete mirabile " of the nephridial duct. After the capsuh 

 is a single row of cells which are disposed in a complicated coil. 

 These cells are perforated by the duct, which is thus, as in th( 

 Oligochaeta, intracellular. In the first set of cells the duct is 

 single, and gives off numerous branchlets into the interior of eacl 

 cell, a condition which has also been observed in many Oligo- 

 chaeta. Afterwards the cells are perforated by two, or even three, 

 main ducts, for the duct returns upon itself and traverses the to\ 



of cells more than once 

 there are also branchlete 

 developed from one 01 

 other of the main ducts 

 The terminal part of th( 

 nephridium is a shor 

 invagination from the 

 exterior, which is line( 

 by cells. There 

 clearly a close resem- 

 blance here with th* 

 nephridium of an Oligo- 

 chaete. The nephridium, 



Fig. 207. Nephridium of Hirudo medicinalis. x 10. 

 (After Bourne.) /, Funnel ; v, distal vesicle. 



however, except for the funnel and the narrow tube immediately 

 following it, does not appear to be ciliated. 



There is, however, some difference of opinion as to the portions 

 of the nephridium where there are two ducts in a single cell. 

 Bourne 2 thinks that where there are two ducts there are two 



1 Loc. cit. 



2 Quart. J. Micr. Sci. xxiv. 1884, p. 419 ; see also ibid, xxxiv. 1893, p. 541 

 which is mainly a criticism of Bolsius' additions to the very considerable litera- 

 ture upon the Leech nephridium. 



