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XVI.  On  the  Anatomy  and  Physiology  of  the  Spongiadce. 
By  J.  S.  Boweebank,  LL.D.,  P.L.8.  &c. 
Eeceived  June  17, — Eead  June  18,  1857. 
PAET  I.— ON  THE  SPICHLA. 
Hithekto  the  Spongiadee  have  been  classified  either  by  their  external  form  or  in  accord- 
ance with  their  chemical  constituents.  In  the  second  edition  of  Lamaeck’s  ‘ Anim.  s. 
Vert.,’  138  species  are  included  in  the  genus  Spongia,  without  the  slightest  reference  to 
their  internal  structure ; and  they  are  diwded  into  seven  groups  by  external  form  only, 
the  same  characters  serving  also,  in  a great  degree,  to  discriminate  the  species. 
Fleiiixg,  GeajN’T,  Johxstox,  and  other  modern  naturahsts,  have  made  their  principal 
dmsions  depend  on  their  chemical  constituents,  and  have  therefore  constructed  three 
great  dmsions  as  genera : — Spongia,  composed  of  keratose  fibres  unmixed,  as  it  was  sup- 
posed, with  earthy  matter;  Halichondria,  formed  principally  of  siliceous  spicula;  and 
Grantia,  ha\ing  the  skeleton  composed  of  calcareous  spicula.  Included  in  the  second  of 
these  divisions  are  the  genera  Tethea,  Geodia,  Pachymatisma,  Spongilla^  Pysidea,  and 
Halisarca,  and  these  nine  genera  are  all  that  are  contained  in  Dr.  Johnston’s  ‘History 
of  British  Sponges.’ 
Both  of  these  arrangements  are  very  insutficient,  and  that  of  Lamaeck  completely 
inefiectual,  inasmuch  as  there  is  no  class  of  animals  in  -which  the  fonn  varies  to  so  great 
an  extent,  according  to  the  difierence  of  locality  or  other  circumstances ; and  also  even 
when  there  is  a strildng  normal  form,  it  is  rarely  thoroughly  developed  until  the  animal 
has  reached  its  full  maturity.  According  to  the  practice  of  Lamaeck,  even  under  the 
most  favourable  circumstances  there  are  frequently  recuiTing  ditficulties  in  the  determi- 
nation of  the  species  by  this  method,  as  the  same  forms  are  found  to  be  common  to  a 
great  number  of  sponges,  the  internal  organization  of  which  are  widely  different  to  each 
other.  From  these  causes  it  is,  that  no  naturalists  with  whom  I have  conferred  on  this 
subject,  have  been  able  to  determine  with  certainty  the  species  of  a sponge  by  the 
description  given  by  Lamaeck  in  his  ‘Anim.  s.  Vert.,’  or  by  those  of  any  other  author 
who  has  adopted  the  same  method  of  description,  with  the  exception  of  perhaps  a few 
very  striking  species. 
The  dmsion  of  the  Spongiadee  by  their  chemical  constituents,  may  serve  very  well  to 
separate  them  into  primary  groups,  but  they  are  far  too  limited  to  be  applied  as  generic 
characters.  I have  therefore  for  this  purpose  rejected  both  systems,  and  have  retained 
the  latter  one  for  the  purpose  of  forming  primary  divisions  only,  and  I purpose  founding 
the  generic  characters  principally  on  the  organic  structure  and  mode  of  arrangement  of 
MDCCCLVIII.  2 Q 
