﻿54 
  THE 
  ZOOLOGIST. 
  

  

  green 
  coating 
  of 
  the 
  fresh-water 
  Sponge 
  (Spongilla 
  lacustris, 
  not 
  

   fluviatilis, 
  as 
  might 
  be 
  supposed), 
  and 
  insect 
  larvae 
  and 
  their 
  

   tubes 
  abound 
  in 
  the 
  gravel. 
  Eels 
  are 
  the 
  only 
  fishes 
  observed. 
  

   A 
  great 
  and 
  unnecessary 
  waste 
  of 
  shell-fish 
  life 
  takes 
  place 
  from 
  

   the 
  primitive 
  methods 
  still 
  used 
  to 
  obtain 
  the 
  pearls, 
  both 
  in 
  

   this 
  species 
  and 
  in 
  the 
  marine 
  forms. 
  Instead 
  of 
  slitting 
  the 
  

   two 
  adductor 
  muscles, 
  or 
  the 
  single 
  one 
  in 
  the 
  Pearl-Oyster, 
  a 
  

   screw-lever 
  can 
  be 
  used 
  for 
  opening 
  the 
  valves 
  sufficiently 
  for 
  

   inspection. 
  The 
  molluscs 
  can 
  thus 
  be 
  returned 
  to 
  the 
  water, 
  and 
  

   may 
  develop 
  another 
  pearl. 
  

  

  Artificial 
  Pearls. 
  — 
  Jaquin 
  made 
  artificial 
  pearls 
  for 
  Catherine 
  

   de 
  Medicis 
  of 
  glass, 
  and 
  with 
  the 
  silvery 
  scales 
  of 
  Gyprinus 
  

   alburnus. 
  Similar 
  artificial 
  pearls 
  were 
  in 
  the 
  London 
  Exhibition 
  

   of 
  1851. 
  At 
  the 
  present 
  time 
  their 
  manufacture 
  by 
  a 
  different 
  

   process 
  is 
  carried 
  out 
  extensively 
  in 
  Paris. 
  

  

  Pearls 
  as 
  Medicine. 
  — 
  Besides 
  ornamental 
  purposes, 
  in 
  olden 
  

   time 
  (a 
  century 
  ago) 
  pearl-powder 
  was 
  used 
  as 
  a 
  medicine 
  for 
  

   many 
  diseases, 
  just 
  as 
  powdered 
  ivory 
  and 
  musk 
  lingered 
  till 
  

   our 
  own 
  day. 
  Some 
  pearls, 
  again, 
  were 
  reduced 
  to 
  powder 
  or 
  

   chunam, 
  to 
  be 
  used 
  with 
  betel-leaf 
  and 
  areca-nut 
  as 
  a 
  masti- 
  

   catory. 
  

  

  Reproduction, 
  — 
  Considerable 
  obscurity 
  still 
  remains 
  in 
  regard 
  

   to 
  the 
  spawning 
  of 
  the 
  Pearl-Oysters. 
  Leon 
  Diguet 
  thinks 
  this 
  

   occurs 
  in 
  autumn. 
  The 
  Japanese 
  Pearl-Oyster, 
  again, 
  spawns 
  

   from 
  June 
  to 
  August.* 
  

  

  Mother-of 
  -Pearl 
  Industry. 
  — 
  A 
  few 
  words 
  may 
  now 
  be 
  said 
  

   about 
  the 
  mother-of-pearl 
  industry. 
  The 
  valves 
  of 
  the 
  various 
  

   Pearl-Oysters 
  are 
  extensively 
  used 
  in 
  papier-mache 
  work, 
  in 
  in- 
  

   laid 
  work, 
  and 
  in 
  the 
  decoration 
  of 
  ecclesiastical 
  vestments 
  in 
  

   Eussia. 
  The 
  Chinese, 
  Siamese, 
  Japanese, 
  and 
  Turks 
  are 
  great 
  

   in 
  inlaid 
  work, 
  and 
  they 
  also 
  employ 
  powder 
  made 
  from 
  Trockus 
  

   and 
  Haliotis. 
  In 
  our 
  own 
  country 
  a 
  large 
  trade 
  is 
  carried 
  on 
  in 
  

   button-making, 
  in 
  the 
  manufacture 
  of 
  breast-pins, 
  earrings, 
  

   cane- 
  and 
  umbrella-handles, 
  card-cases, 
  boxes, 
  studs, 
  napkin- 
  

   rings 
  (Trockus), 
  artificial 
  catseyes, 
  and 
  beads. 
  Cameos 
  are 
  also 
  

   carved 
  on 
  mother-of-pearl 
  shells 
  (such 
  as 
  the 
  dark 
  varieties, 
  e.g. 
  

  

  * 
  Prof. 
  Herdrnan's 
  observations 
  (op. 
  cit. 
  pp. 
  125, 
  126) 
  would 
  seem 
  to 
  

   point 
  to 
  May 
  as 
  the 
  central 
  spawning 
  month, 
  though 
  many 
  may 
  spawn 
  

   earlier 
  and 
  later, 
  as 
  with 
  the 
  Common 
  Mussel. 
  

  

  

  