﻿on 
  a 
  new 
  species 
  of 
  the 
  genus 
  haplotaxis. 
  311 
  

  

  Nephridia 
  and 
  Genital 
  Ducts. 
  

  

  From 
  the 
  point 
  of 
  view 
  of 
  general 
  morphology, 
  this 
  new 
  

   species 
  of 
  Haplotaxis 
  is 
  of 
  considerable 
  interest 
  owing 
  to 
  

   the 
  remarkable 
  structural 
  similarity 
  that 
  exists 
  between 
  the 
  

   sperm-duct 
  and 
  the 
  nephridium. 
  The 
  genus 
  belongs 
  to 
  that 
  

   section 
  of 
  the 
  Oligoch^eta 
  which 
  in 
  former 
  days 
  were 
  termed 
  

   " 
  Limicoline 
  " 
  or 
  Microdrili 
  (mihi), 
  in 
  which 
  excretory 
  

   segmental 
  organs 
  are 
  in 
  the 
  mature 
  worm 
  absent 
  from 
  the 
  

   segments 
  containing 
  the 
  genital 
  ducts. 
  This 
  distinction 
  is 
  no 
  

   longer 
  of 
  so 
  much 
  importance 
  now-a-days, 
  since 
  Vejdovsky 
  (15) 
  

   has 
  shown 
  that 
  in 
  several 
  families, 
  viz. 
  the 
  Chaetogastridge, 
  

   Naidida3, 
  Enchytra3ida3, 
  Tubificidte, 
  and 
  Lumbricididaa, 
  these 
  

   nephridia 
  are 
  present 
  in 
  the 
  genital 
  segments 
  of 
  the 
  innnature 
  

   worm, 
  but 
  disappear 
  by 
  degeneration 
  before 
  tbe 
  genital 
  ducts 
  

   make 
  their 
  appearance 
  ; 
  and 
  Forbes 
  (4) 
  states 
  that 
  in 
  H. 
  

   emissarius 
  ( 
  = 
  H. 
  gordioides) 
  the 
  anterior 
  nephridia 
  in 
  

   Segments 
  X 
  to 
  XV 
  are 
  small 
  and 
  rudimentary. 
  Now 
  the 
  

   questions 
  that 
  naturally 
  arise 
  in 
  connection 
  with 
  Haplotaxis 
  

   heterogyne 
  are 
  : 
  (1) 
  Do 
  nephridia 
  exist 
  in 
  the 
  immature 
  

   worm 
  in 
  Segments 
  X, 
  XI 
  ? 
  If 
  so, 
  then 
  (2) 
  have 
  they 
  disap- 
  

   peared 
  in 
  these 
  segments 
  and 
  been 
  replaced 
  by 
  the 
  sperm- 
  

   ducts, 
  which 
  have 
  assumed 
  the 
  structure 
  of 
  nephridia 
  ? 
  Or, 
  

   on 
  the 
  other 
  hand 
  (3) 
  have 
  the 
  nephridia 
  persisted 
  in 
  these 
  

   two 
  segments 
  and 
  been 
  converted 
  functionally 
  into 
  the 
  

   sperm-ducis 
  ? 
  As 
  we 
  have 
  no 
  knowledge 
  of 
  the 
  develop- 
  

   mental 
  history 
  of 
  any 
  species 
  of 
  Haplotaxis, 
  we 
  cannot 
  give 
  

   a 
  direct 
  or 
  certain 
  answer 
  to 
  either 
  of 
  these 
  questions, 
  but 
  

   the 
  striking 
  similarity 
  between 
  the 
  two 
  categories 
  of 
  organs 
  

   presented 
  by 
  this 
  species 
  make 
  it 
  scarcely 
  probable 
  that 
  the 
  

   sperm-ducts 
  have 
  assumed 
  the 
  structure 
  of 
  nephridia, 
  and 
  

   renders 
  it 
  much 
  more 
  probable 
  that 
  the 
  nephridia 
  have 
  been 
  

   converted 
  into 
  sperm-ducts, 
  the 
  minute 
  anatomy 
  of 
  which 
  is 
  

   so 
  absolutely 
  unlike 
  that 
  presented 
  by 
  these 
  organs 
  in 
  other 
  

   Oligochaetes. 
  The 
  small 
  degree 
  of 
  structural 
  difference 
  

   between 
  the 
  two 
  organs 
  in 
  the 
  present 
  worm 
  may 
  be 
  due 
  to 
  

   the 
  difference 
  in 
  function. 
  If 
  this 
  third 
  question 
  be 
  answered 
  

  

  