﻿27 
  

  

  SOME 
  EEMARKS 
  WITH 
  REGAED 
  TO 
  PROFESSOR 
  BOURNE'S 
  

   MONOGRAPH 
  ON 
  THE 
  NERITID^. 
  

  

  By 
  Dr. 
  H. 
  Simeoth. 
  

  

  Bead 
  Uth 
  JSfovember, 
  1909. 
  

  

  We 
  owe 
  many 
  thanks 
  to 
  Professor 
  Bourne 
  for 
  his 
  most 
  accurate 
  

   study 
  of 
  the 
  interesting 
  family 
  of 
  the 
  Neritid®.^ 
  It 
  is 
  in 
  no 
  way 
  

   my 
  intention 
  to 
  criticize 
  any 
  of 
  the 
  many 
  facts 
  brought 
  forward 
  

   by 
  him. 
  But 
  as 
  I 
  think 
  I 
  can 
  give 
  in 
  several 
  directions 
  another 
  

   interpretation, 
  which 
  may 
  perhaps 
  clear 
  up 
  the 
  various 
  difficulties 
  

   he 
  finds 
  in 
  the 
  problem, 
  I 
  ask 
  for 
  permission 
  to 
  do 
  so. 
  

  

  Professor 
  Bourne 
  unites 
  all 
  the 
  forms 
  of 
  the 
  great 
  family 
  in 
  one 
  

   genus, 
  Nerita, 
  which 
  he 
  divides 
  into 
  the 
  four 
  sections 
  Nerita, 
  s.s., 
  

   Parmierita, 
  Septaria, 
  and 
  Neritina. 
  Here 
  I 
  may 
  remark 
  that 
  Schep- 
  

   man- 
  divides 
  the 
  group 
  into 
  two 
  families, 
  Neritacea 
  and 
  Neritilidae, 
  

   on 
  conchological 
  characters, 
  the 
  Neritilidse 
  comprising 
  the 
  genera 
  

   Neritilia 
  and 
  Septaria. 
  I 
  should 
  prefer 
  the 
  anatomical 
  division 
  of 
  

   Boume. 
  As 
  it 
  is 
  founded 
  in 
  the 
  first 
  place 
  upon 
  the 
  genital 
  organs 
  

   I 
  will 
  begin 
  with 
  those. 
  

  

  Professor 
  Bourne 
  has 
  had 
  only 
  female 
  individuals 
  of 
  Septaria, 
  but 
  

   both 
  sexes 
  of 
  all 
  the 
  other 
  genera. 
  I 
  think 
  I 
  can 
  explain 
  the 
  cause 
  

   of 
  the 
  absence 
  of 
  males. 
  When 
  I 
  once 
  had 
  a 
  series 
  of 
  about 
  thirty 
  

   specimens 
  of 
  an 
  undetermined 
  species 
  of 
  Septaria, 
  all 
  the 
  large 
  

   individuals 
  proved 
  to 
  be 
  females, 
  the 
  males 
  being 
  small, 
  only 
  about 
  

   half 
  the 
  diameter. 
  Therefore 
  it 
  may 
  be 
  presumed 
  that 
  in 
  this 
  genus 
  

   the 
  males 
  are 
  dwarfed. 
  Future 
  investigation 
  will 
  have 
  to 
  decide 
  

   whether 
  the 
  genus 
  is 
  hermaphroditic 
  and 
  proterandrous, 
  developing 
  

   first 
  the 
  male 
  and 
  afterwards 
  the 
  female 
  organs, 
  as 
  is 
  the 
  case 
  with 
  

   many 
  Pulmonata, 
  or 
  if 
  the 
  proterandric 
  condition 
  was 
  a 
  character 
  of 
  

   a 
  hypothetical 
  ancestor, 
  the 
  sexes 
  being 
  individually 
  separated 
  as 
  at 
  

   present. 
  

  

  I 
  will 
  now 
  give 
  the 
  explanation 
  of 
  the 
  compound 
  structure 
  of 
  

   the 
  genitalia. 
  They 
  differ 
  widely 
  from 
  all 
  Prosobranchs. 
  But 
  I 
  do 
  

   not 
  find 
  any 
  difficulty 
  in 
  compaiing 
  them 
  with 
  those 
  of 
  the 
  Pul- 
  

   monata. 
  Professor 
  Bourne 
  regards 
  the 
  ovar)' 
  and 
  tlie 
  testis, 
  the 
  

   oviduct 
  and 
  the 
  sperm-duct, 
  as 
  homologous 
  organs. 
  I 
  shall 
  endeavour 
  

   to 
  explain 
  the 
  homologies 
  as 
  completely 
  as 
  possible. 
  

  

  Female 
  Organs. 
  

   Bourne 
  nses 
  the 
  very 
  good 
  expression 
  ' 
  ootype 
  ' 
  for 
  uterus, 
  thus 
  

   indicating 
  the 
  descent 
  from 
  the 
  Platodes. 
  It 
  is 
  the 
  female 
  part 
  

   of 
  the 
  Pulmonata 
  — 
  sperm-oviduct 
  or 
  uterus. 
  The 
  vitelline 
  gland 
  

  

  1 
  G. 
  Bourne, 
  " 
  Contributions 
  to 
  the 
  Morphology 
  of 
  the 
  group 
  Neritacea 
  of 
  Aspido- 
  

   branch 
  Gastropods." 
  Part 
  I 
  : 
  The 
  Neritidnc. 
  Proc. 
  Zool. 
  Soc. 
  Loudon, 
  1908, 
  

   pp. 
  810-87, 
  pis. 
  xlvi-lxvi, 
  and 
  1 
  text-fig. 
  

  

  - 
  M. 
  M. 
  Schepman, 
  "The 
  Prosobrauchia 
  of 
  the 
  Siboga-Expedition." 
  Part 
  I: 
  

   Rbipidoglossa 
  and 
  Docoglossa. 
  

  

  