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XXXVII.  On  the  Structure  and  Functions  of  the  Hairs  of  the  Crustacea.  By  Campbell 
De  Moegaat,  Surgeon  to  the  Middlesex  Hospital.  Communicated  by  Geoege  Busk,  Esq. 
Received  Marcli  13, — Read  April  29,  1858. 
The  observations  of  M.  Lavalle* * * §  on  the  structure  of  the  hairs  attached  to  the  shell 
of  the  decapodous  Crustacea,  have  shown  that  these  organs  are  not  mere  appendages 
to  the  shell,  as  was  formerly  supposed  (see  SiEBOLuf),  but  that  they  are  sometimes 
connected  with  canals  which  penetrate  its  whole  thickness,  in  such  a manner  that  there 
seems  to  be  a continuity  of  the  material  which  fills  the  hair  with  that  which  exists  in 
the  corresponding  canal.  The  hairs  are  traversed  by  a canal ; at  their  base  they  expand 
into  a hulb,  which  is  received  into  a cup-shaped  cavity  in  the  outer  pigmentary  layer 
of  the  shell,  and  which  is  limited  to  that  part,  never  being  prolonged  into  the  inner 
layers  of  the  shell.  This  cup-shaped  cavity  is  the  termination  of  a canal  which  traverses 
the  entire  thickness  of  the  shell,  and  is  here  expanded  so  as  to  enclose  the  bulb.  The 
canal  of  the  hair  is  enlarged  at  the  situation  of  the  bulb.  It  is  then  constricted,  but  it 
opens  below  into  its  receiving  cavity,  and  is  continuous  with  the  canal  of  the  shell. 
M.  Hollaed  J,  who  has  investigated  the  structures  of  the  hairs  in  many  of  the  articu- 
lated classes,  finds  that  there  exists  in  them  the  same  general  character  of  being  hollow 
organs  connected  with  canals  channeled  out  in  the  hard  tegumentary  coverings  of  the 
body. 
Of  the  hairs  of  the  Crustacea,  especially,  he  says  that  the  canals  of  the  shell  which 
correspond  to  the  hairs  are  occupied  by  membranous  investments,  which  embrace  the 
base  of  the  hairs,  and  constitute  follicular  sacs,  terminating  inferiorly  in  a conical  extre- 
mity ; and  that  they  seem  to  receive  through  it  a nutrient  system,  of  which  the  debris 
are  easily  recognized  in  most  preparations. 
The  general  conclusions  at  which  he  arrives  with  regard  to  insects,  indicate,  though 
vaguely,  that  these  organs  may  be,  amongst  other  functions,  connected  with  general 
sensation  §. 
* Annales  des  Sciences  Naturelles,  1847. 
t Anatomy  of  the  Invertebrata. — “ The  tubules,  points,  bristles,  single  and  bifid  hairs,  which  are  usually 
hollow,  and  exist  on  the  surface  or  borders  of  the  ditferent  parts  of  the  cutaneous  skeleton,  are  always  mere 
prolongations  or  simple  excrescences  of  the  integument,  and  contain  its  characteristic  substance — chitine.” 
— Bennett’s  Translation,  p.  310. 
X Revue  et  Magasin  de  Zoologie,  1851. 
§ “ Enfin,  nettement  limites  par  leur  base  d’implantation,  revetant  la  forme  d’un  pedicule  etroit  ou  d’lm 
renflement,  les  pods  et  les  ecailles  des  entomozoaires  sont  toujours  re9us  dans  de  petits  sacs : et,  chez  un 
certain  nombre  d’especes,  on  voit  facilement,  que  ces  sacs,  veritables  foUicules,  re9oivent  par  leur  fond  ou 
MDCCCLVm.  6 A 
