﻿ANATOMY 
  AND 
  AFFINITIES 
  OF 
  THE 
  TEOOHID^. 
  57 
  

  

  vessels 
  bi-inging 
  blo(xi 
  from 
  the 
  lacunas 
  of 
  the 
  auterior 
  por- 
  

   tiou 
  ol 
  the 
  mantle 
  and 
  the 
  perirectal 
  sinus. 
  This 
  vein 
  then 
  

   runs 
  along 
  the 
  branchial 
  support, 
  distributing 
  blood 
  to 
  the 
  

   lamella3 
  of 
  the 
  gill, 
  constituting 
  in 
  fact 
  the 
  afferent 
  

   branchial 
  vein. 
  Part 
  of 
  the 
  blood 
  conveyed 
  by 
  the 
  trans- 
  

   verse 
  pallial 
  vein 
  is 
  distributed 
  directly 
  to 
  the 
  left 
  kidney 
  by 
  

   two 
  sinuses 
  (fig. 
  42) 
  arising 
  from 
  that 
  vein 
  as 
  it 
  crosses 
  over 
  

   the 
  rectum 
  and 
  emerges 
  between 
  the 
  renal 
  apertures. 
  These 
  

   sinuses 
  follow 
  the 
  right 
  and 
  left 
  borders 
  of 
  the 
  papillary 
  sac, 
  

   and 
  communicate 
  with 
  the 
  lacuna) 
  of 
  that 
  organ. 
  The 
  blood, 
  

   after 
  passing 
  through 
  the 
  lacunas 
  of 
  fclie 
  papillary 
  sac, 
  is 
  col- 
  

   lected 
  into 
  a 
  small 
  vessel 
  which 
  communicates 
  directly 
  with 
  

   the 
  left 
  auricle. 
  After 
  aeration, 
  the 
  venous 
  blood 
  distributed 
  

   to 
  the 
  gill 
  is 
  collected 
  into 
  a 
  large 
  efferent 
  branchial 
  vein 
  

   (figs. 
  39 
  — 
  43, 
  e. 
  h. 
  v.), 
  which 
  runs 
  along 
  the 
  base 
  of 
  the 
  gill 
  

   and 
  conveys 
  the 
  arterialised 
  blood 
  to 
  the 
  left 
  auricle. 
  

  

  The 
  right 
  auricle 
  also 
  communicates 
  with 
  the 
  lacunae 
  of 
  

   the 
  papillav}^ 
  sac, 
  receiving 
  some 
  of 
  the 
  venous 
  blood 
  passing 
  

   through 
  that 
  organ. 
  In 
  consequence 
  of 
  the 
  suppression 
  of 
  

   the 
  right 
  gill 
  there 
  is 
  no 
  functional 
  efferent 
  branchial 
  vessel 
  

   communicating 
  with 
  the 
  right 
  auricle, 
  though 
  it 
  is 
  possible 
  

   that 
  a 
  very 
  small 
  vessel 
  which 
  runs 
  on 
  the 
  mantle-wall 
  under- 
  

   neath 
  the 
  rectum 
  and 
  communicates 
  with 
  the 
  right 
  auricle 
  

   may, 
  according 
  to 
  Thiele 
  (41), 
  represent 
  a 
  vestige 
  of 
  the 
  right 
  

   efferent 
  branchial 
  vein. 
  

  

  Nervous 
  System. 
  — 
  The 
  nervous 
  system 
  of 
  the 
  Trochidee 
  

   presents 
  no 
  differences 
  of 
  importance 
  in 
  any 
  of 
  the 
  species 
  so 
  

   far 
  examined. 
  Such 
  forms 
  as 
  T. 
  striatus, 
  T. 
  tumidus, 
  etc., 
  

   being 
  far 
  too 
  small 
  for 
  satisfactory 
  results 
  to 
  be 
  obtained 
  by 
  

   dissection, 
  were 
  embedded 
  in 
  paraffin 
  wax 
  and 
  cut 
  into 
  serial 
  

   sections, 
  and 
  from 
  an 
  examination 
  of 
  these 
  sections 
  the 
  main 
  

   features 
  of 
  their 
  anatomy 
  were 
  subsequently 
  made 
  out, 
  the 
  

   nervous 
  system 
  being 
  reconstructed 
  by 
  the 
  method 
  of 
  build- 
  

   ing 
  up 
  in 
  wax. 
  

  

  The 
  distribution 
  of 
  nerve-cells 
  is 
  of 
  particular 
  interest. 
  In 
  

   Pleurotomaria 
  there 
  is 
  a 
  very 
  general 
  distribution 
  of 
  nerve- 
  

   cells 
  throughout 
  a 
  greater 
  part 
  of 
  the 
  nervous 
  system 
  (Wood- 
  

  

  VOL. 
  48, 
  PART 
  1. 
  MEW 
  SERIKS. 
  5 
  

  

  