﻿42 
  THE 
  ZOOLOGIST. 
  

  

  dew, 
  or, 
  as 
  others 
  more 
  poetically 
  termed 
  them, 
  "tears 
  of 
  the 
  

   Nereids." 
  Columbus, 
  therefore, 
  on 
  discovering 
  the 
  coast 
  of 
  

   Paria,* 
  thought 
  he 
  had 
  fallen 
  on 
  the 
  right 
  place 
  for 
  pearls, 
  as 
  

   the 
  trees 
  grew 
  with 
  their 
  roots 
  in 
  the 
  sea, 
  and 
  these 
  roots 
  were 
  

   covered 
  with 
  Oysters 
  ready 
  to 
  receive 
  dewdrops 
  from 
  the 
  leaves 
  

   above 
  them. 
  iElian, 
  on 
  the 
  other 
  hand, 
  thought 
  they 
  were 
  

   formed 
  by 
  a 
  flash 
  of 
  lightning 
  in 
  the 
  open 
  shells. 
  Even 
  now 
  

   there 
  are 
  differences 
  of 
  opinion 
  as 
  to 
  their 
  origin, 
  some 
  (after 
  

   Rondelet) 
  considering 
  the} 
  7 
  arise 
  from 
  a 
  diseased 
  condition 
  of 
  the 
  

   shell-fish, 
  such, 
  for 
  instance, 
  as 
  produces 
  gall-stones 
  or 
  other 
  

   morbid 
  deposits 
  ; 
  others, 
  after 
  Reaumur 
  (and 
  Profs. 
  H. 
  Merkel,t 
  

   Mobius, 
  and 
  Grand, 
  \ 
  who 
  followed 
  him), 
  to 
  an 
  abnormal 
  con- 
  

   cretion, 
  or 
  an 
  abundant 
  secretion 
  of 
  the 
  nacreous 
  material 
  ; 
  

   to 
  the 
  entrance 
  of 
  a 
  grain 
  of 
  sand 
  (Stenone, 
  Piedi, 
  and 
  Count 
  de 
  

   Bournon, 
  followed 
  by 
  De 
  Blainville§) 
  ; 
  or 
  calcareous 
  crystals, 
  

   organic 
  debris, 
  and 
  amorphous 
  bodies 
  between 
  the 
  shell 
  and 
  the 
  

   mantle 
  ; 
  to 
  the 
  irritation 
  caused 
  by 
  a 
  parasite 
  (De 
  Filippi, 
  

   Distoma 
  duplication, 
  and 
  other 
  forms 
  in 
  fresh-water 
  pearls 
  ; 
  Kiich- 
  

   enmeister, 
  water-mite 
  — 
  De 
  Filippi 
  comparing 
  them 
  with 
  galls) 
  ; 
  

   by 
  an 
  egg 
  of 
  the 
  Mussel 
  itself 
  (Sir 
  E. 
  Home|j), 
  or 
  that 
  of 
  a 
  para- 
  

   site. 
  Kiichenmeister 
  found 
  cysts 
  enclosing 
  larvae 
  of 
  Atax 
  (a 
  

   mite) 
  in 
  M. 
  margaritana 
  ,- 
  Mobius, 
  remains 
  of 
  Trematodes 
  in 
  

   pearls 
  from 
  the 
  same 
  species 
  ; 
  KelaartH 
  showed 
  the 
  importance 
  

   of 
  parasites 
  in 
  such 
  formations 
  in 
  M. 
  vulgaris, 
  a 
  view 
  confirmed 
  

   by 
  Thurston 
  ; 
  and 
  Garner** 
  observed 
  that 
  the 
  pearls 
  in 
  the 
  

   Common 
  Mussel 
  were 
  due 
  to 
  Distomids. 
  The 
  same 
  opinion 
  was 
  

   advanced 
  by 
  Cornba, 
  Giard, 
  and 
  quite 
  recently 
  (1901) 
  by 
  Dubois. 
  

   The 
  view 
  that 
  they 
  are 
  allied 
  to 
  sedimentary 
  concretions, 
  

   again, 
  was 
  brought 
  forward 
  by 
  Dr. 
  George 
  Harley.tt 
  who 
  

   thought 
  them 
  similar 
  in 
  structure 
  to 
  mineral 
  nodules 
  of 
  wavel- 
  

  

  I'. 
  L. 
  Simiuonds, 
  ' 
  Commercial 
  Products 
  of 
  the 
  Sea.' 
  London, 
  1879, 
  

   p. 
  421. 
  Much 
  interesting 
  information 
  will 
  be 
  found 
  in 
  this 
  work. 
  

  

  •( 
  " 
  JMikrogeologie 
  " 
  in 
  ' 
  Froriep's 
  Notizen,' 
  1857, 
  i. 
  Bd. 
  no. 
  2, 
  p. 
  18. 
  

   ;[ 
  " 
  Methode 
  de 
  cult, 
  de 
  l'Huitre 
  Perliere," 
  ' 
  Eev. 
  Marit. 
  et 
  Colon. 
  Ann.' 
  

   1895. 
  

  

  i 
  ' 
  Diet. 
  Sc. 
  Nat.' 
  vol. 
  xxviii. 
  p. 
  505. 
  

  

  ' 
  Philos. 
  Trans.' 
  1826. 
  

   If 
  ' 
  Ann. 
  Nat. 
  Hist.' 
  third 
  ser. 
  i. 
  p. 
  81. 
  

   ** 
  ' 
  Proc. 
  Linn. 
  Soc, 
  Zool.,' 
  xi. 
  p. 
  426, 
  1871. 
  

   If 
  ' 
  Proceed. 
  E. 
  S.' 
  xlv. 
  p. 
  613. 
  

  

  