﻿Structure 
  of 
  Magelona. 
  427 
  

  

  projected 
  from 
  the 
  edge 
  of 
  the 
  snout 
  in 
  a 
  specimen 
  apparently 
  

   undergoing 
  repair 
  after 
  injury*. 
  

  

  II. 
  The 
  Muscular 
  System. 
  

  

  Head. 
  — 
  The 
  muscular 
  system 
  of 
  the 
  snout 
  consists 
  of 
  a 
  

   median 
  and 
  a 
  lateral 
  pair 
  of 
  longitudinal 
  muscles. 
  

  

  The 
  median 
  form 
  symmetrical 
  muscles 
  which 
  stretch 
  from 
  

   the 
  tip 
  of 
  the 
  snout 
  (in 
  advance 
  of 
  the 
  lateral) 
  to 
  the 
  mouth. 
  

   Viewed 
  from 
  above 
  the 
  fibres 
  slant 
  backward 
  and 
  inward 
  

   toward 
  the 
  middle 
  line 
  throughout 
  the 
  greater 
  part 
  of 
  the 
  

   muscles 
  ; 
  but 
  after 
  they 
  separate 
  posteriorly 
  the 
  direction 
  of 
  

   the 
  fibres 
  is 
  more 
  nearly 
  transverse 
  — 
  slanting 
  from 
  above 
  

   downward 
  and 
  inward 
  at 
  a 
  wide 
  angle 
  and 
  as 
  a 
  boldly 
  

   marked 
  series. 
  If 
  a 
  transverse 
  section 
  be 
  made 
  at 
  the 
  very 
  

   tip 
  of 
  the 
  snout, 
  the 
  area 
  is 
  hypodermic 
  and 
  cuticular, 
  with 
  

   the 
  exception 
  of 
  two 
  small 
  oval 
  regions 
  representing 
  the 
  

   attachments 
  of 
  these 
  muscles, 
  which 
  are 
  widely 
  separated 
  by 
  

   a 
  hypodermic 
  wedge. 
  The 
  latter 
  gradually 
  diminishes, 
  so 
  

   that 
  by-and-by 
  the 
  section 
  of 
  the 
  central 
  muscles 
  has 
  the 
  

   aspect 
  of 
  a 
  pair 
  of 
  spectacles, 
  the 
  muscles 
  forming 
  the 
  eyes 
  

   and 
  the 
  nasal 
  bridge 
  being 
  represented 
  by 
  the 
  chitinous 
  

   connecting-bar, 
  which 
  is 
  continuous 
  with 
  the 
  investment 
  of 
  

   each 
  muscle. 
  

  

  As 
  the 
  chitinous 
  basement-tissue 
  just 
  mentioned 
  is 
  of 
  

   considerable 
  functional 
  importance 
  in 
  the 
  snout, 
  it 
  may 
  be 
  

   well 
  to 
  describe 
  its 
  arrangement 
  before 
  proceeding 
  further 
  

   with 
  the 
  muscles 
  with 
  which 
  it 
  is 
  intimately 
  associated. 
  As 
  

   indicated, 
  the 
  chitinous 
  supports 
  in 
  this 
  region 
  of 
  the 
  snout 
  

   form 
  for 
  each 
  muscle 
  a 
  complete 
  investment, 
  which, 
  more- 
  

   over, 
  is 
  connected 
  with 
  its 
  fellow 
  by 
  a 
  median 
  bar 
  ; 
  while 
  

   from 
  the 
  outer 
  edge 
  of 
  the 
  chitinous 
  rim 
  a 
  thin 
  lamella 
  passes 
  

   outward 
  to 
  the 
  tip 
  of 
  the 
  hypodermic 
  expansion, 
  and 
  there- 
  

   fore 
  represents 
  the 
  claspers 
  or 
  limbs 
  of 
  the 
  spectacles 
  (in 
  

   transverse 
  section). 
  By-and-by 
  (proceeding 
  backward) 
  a 
  

  

  * 
  In 
  these 
  days 
  of 
  elaborate 
  instrumental 
  aids 
  it 
  is 
  well 
  to 
  mention 
  

   that, 
  though 
  the 
  majority 
  of 
  such 
  appliances 
  were 
  at 
  command, 
  nothing 
  

   better 
  has 
  been 
  found 
  than 
  the 
  following 
  simple 
  method 
  of 
  examining 
  

   the 
  structure 
  of 
  such 
  forms 
  in 
  the 
  prepared 
  state: 
  — 
  The 
  specimens 
  are 
  

   placed 
  in 
  absolute 
  alcohol, 
  fitted 
  to 
  very 
  fine 
  corks, 
  again 
  immersed 
  with 
  

   the 
  latter 
  in 
  alcohol, 
  cut 
  in 
  the 
  hand 
  with 
  a 
  keen 
  razor, 
  and 
  mounted 
  in 
  

   chloride 
  of 
  calcium. 
  Dexterity 
  will 
  not, 
  as 
  a 
  rule, 
  enable 
  the 
  observer 
  to 
  

   make 
  trustworthy 
  researches 
  on 
  badly 
  prepared 
  examples 
  of 
  the 
  Annelida. 
  

   If 
  the 
  tissues 
  are 
  so 
  soft 
  that 
  the 
  pressure 
  of 
  the 
  thin 
  glass 
  cover 
  injures 
  

   them, 
  it 
  is 
  sometimes 
  convenient 
  to 
  mount 
  them 
  with 
  a 
  very 
  fine 
  section 
  

   of 
  the 
  cork 
  in 
  a 
  suitable 
  position. 
  

  

  