﻿86 
  PROCEEDINGS 
  OF 
  THE 
  MALACOLOGICAL 
  SOCIETY. 
  

  

  The 
  mating 
  of 
  the 
  red 
  form 
  with 
  the 
  normal 
  always 
  produces 
  

   dark 
  offspring, 
  and 
  if 
  two 
  of 
  these 
  dark 
  ones 
  are 
  mated 
  red 
  progeny 
  

   results. 
  Continual 
  mating 
  of 
  the 
  red 
  considerably 
  improves 
  the 
  

   brilliance 
  of 
  colour. 
  

  

  For 
  the 
  study 
  of 
  tlie 
  freshwater 
  snails 
  small 
  aquaria 
  are 
  not 
  to 
  

   be 
  recommended.' 
  I 
  find 
  the 
  best 
  results 
  are 
  obtained 
  with 
  a 
  bell 
  

   glass 
  nearly 
  30 
  inches 
  in 
  diameter, 
  the 
  bottom 
  filled 
  with 
  a 
  mixture 
  

   of 
  sand 
  and 
  shell 
  grit 
  up 
  to 
  where 
  the 
  sides 
  become 
  vertical, 
  leaving 
  

   a 
  depth 
  of 
  about 
  20 
  inches 
  of 
  water. 
  Such 
  an 
  aquarium 
  should 
  

   contain 
  well-established 
  and 
  growing 
  plants, 
  Vallisneria 
  for 
  choice, 
  

   and 
  should 
  be 
  capable 
  of 
  being 
  rotated 
  or 
  inspected 
  all 
  round. 
  

  

  During 
  the 
  warm 
  weather 
  Planorhis 
  corneus 
  will 
  devour 
  incredible 
  

   quantities 
  of 
  animal 
  food, 
  and 
  it 
  will 
  grow 
  faster 
  and 
  thrive 
  better 
  

   on 
  a 
  flesh 
  diet 
  than 
  on 
  vegetation. 
  I 
  have 
  fed 
  it 
  upon 
  animal 
  food 
  

   exclusively, 
  tough 
  muscular 
  table 
  scraps, 
  and 
  I 
  have 
  made 
  every 
  

   effort 
  to 
  deprive 
  it 
  of 
  plant 
  food, 
  and 
  in 
  such 
  circumstances 
  it 
  

   thrived 
  exceedingly 
  well 
  and 
  attained 
  a 
  large 
  size. 
  

  

  The 
  circumstance 
  of 
  thread-spinning 
  can 
  be 
  observed 
  and 
  studied 
  

   with 
  success 
  if 
  a 
  lai'ge 
  aquarium 
  is 
  used. 
  A 
  self-supporting 
  vessel 
  is 
  

   essential, 
  for 
  the 
  water 
  must 
  not 
  be 
  disturbed, 
  and 
  the 
  growing 
  

   plants 
  must 
  be 
  in 
  sufficient 
  profusion 
  to 
  keep 
  the 
  water 
  from 
  

   becoming 
  foul 
  with 
  a 
  snail 
  population 
  of 
  100 
  or 
  more 
  adults. 
  When 
  

   the 
  snails 
  have 
  settled 
  down, 
  put 
  in 
  one 
  large 
  piece 
  of 
  meat 
  — 
  more 
  

   than 
  is 
  likely 
  to 
  be 
  consumed 
  under 
  two 
  or 
  three 
  days 
  — 
  or 
  renew 
  

   a 
  smaller 
  amount 
  in 
  exactly 
  the 
  same 
  place 
  witliout 
  disturbing 
  the 
  

   plants. 
  Soon 
  a 
  vertical 
  thread 
  will 
  be 
  seen 
  reaching 
  from 
  bottom 
  to 
  

   top, 
  and 
  probably 
  more 
  or 
  less 
  attached 
  at 
  intervals 
  to 
  some 
  upright 
  

   leaf 
  of 
  ValUsneria. 
  This 
  thread 
  will 
  be 
  observed 
  to 
  gradually 
  

   thicken 
  as 
  each 
  snail 
  in 
  passing 
  along 
  it 
  adds 
  its 
  contribution 
  of 
  

   slimy 
  matter, 
  and 
  in 
  quite 
  a 
  short 
  time 
  a 
  rope 
  of 
  respectable 
  

   proportions 
  is 
  formed, 
  leading 
  from 
  the 
  unconsumed 
  meat 
  to 
  the 
  

   surface 
  of 
  the 
  water, 
  where 
  many 
  ramifications 
  will 
  be 
  found. 
  It 
  

   is 
  interesting 
  to 
  watch 
  a 
  snail 
  leisurely 
  travelling 
  at 
  the 
  surface 
  

   come 
  into 
  contact 
  with 
  one 
  of 
  the 
  surface 
  ramification 
  lines. 
  In 
  an 
  

   instant 
  it 
  becomes 
  alert 
  and 
  quickens 
  its 
  pace; 
  there 
  is 
  never 
  

   a 
  mistake 
  as 
  to 
  the 
  direction, 
  and 
  in 
  a 
  little 
  time 
  the 
  snail 
  reaches 
  

   the 
  thick 
  vertical 
  rope 
  and 
  commences 
  its 
  descent. 
  

  

  Planorhis 
  corneus, 
  as 
  is 
  well 
  known, 
  can 
  rise 
  to 
  the 
  surface 
  from 
  

   the 
  bottom 
  like 
  a 
  cork, 
  or 
  sink 
  like 
  a 
  stone, 
  and 
  it 
  apparently 
  has 
  

   considerable 
  control 
  over 
  the 
  rate 
  of 
  fall 
  and 
  rise. 
  In 
  a 
  deep 
  

   aquarium 
  a 
  falling 
  snail 
  will 
  frequently 
  retard 
  its 
  progress 
  very 
  

   perceptibly 
  as 
  it 
  nears 
  the 
  bottom, 
  and 
  a 
  rising 
  snail 
  will 
  often 
  carry 
  

   a 
  piece 
  of 
  meat 
  more 
  than 
  its 
  own 
  weight, 
  without 
  any 
  visible 
  

   difference 
  to 
  the 
  normal 
  rate 
  of 
  ascension, 
  which 
  shows 
  there 
  must 
  

   be 
  a 
  considerable 
  latitude 
  of 
  power. 
  I 
  was, 
  fortunately, 
  able 
  a 
  few 
  

   days 
  ago 
  to 
  observe 
  a 
  specimen 
  of 
  corneus 
  in 
  its 
  second 
  year 
  gently 
  

   drop 
  about 
  9 
  or 
  10 
  inches 
  below 
  the 
  water 
  surface; 
  it 
  came 
  to 
  a 
  

   momentary 
  halt, 
  and 
  then 
  floated 
  back 
  to 
  the 
  surface. 
  In 
  this 
  

   instance 
  there 
  was 
  no 
  interference 
  in 
  any 
  way, 
  and 
  the 
  snail 
  had 
  no 
  

   assistance 
  from 
  a 
  spun 
  thread. 
  This 
  is 
  the 
  only 
  case 
  I 
  have 
  seen. 
  

  

  