AND  PHYSIOLOGY  OP  THE  SPONGIAD^. 
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true  and  the  pseudo-connecting  spicula,  if  we  may  so  term  them ; the  proportions  of  the 
former  are  generally  stout  and  strong,  while  those  of  the  latter  are  always  long  and  very 
much  more  slender. 
Spiculated  poekecto-teknate. — Having  three  equidistant  porrect  terminal  rays,  and 
a fourth  or  central  one  in  a line  with  the  axis  of  the  shaft  (Plate  XXIII.  fig.  49).  From 
Geodia  Barretti,  Boweebank,  MS.,  from  Vigten  Island,  Norway. 
Spiculated  EECUEVO-TEEisrATE. — Having  three  equidistant  recurved  radii,  and  the  cen- 
tral terminal  one  porrect  in  the  line  of  the  axis  of  the  shaft  of  the  spiculum  (Plate  XXHI. 
fig.  50).  From  Geodia  Barretti,  Boweebajstk,  MS.,  from  Vigten  Island,  coast  of  Norway. 
The  central  porrect  terminal  ray  is  often  more  or  less  deflected  from  the  axial  line  of 
the  shaft,  as  in  Plate  XXHI.  fig.  51 ; and  occasionally,  in  the  simple  recurvo-temate 
form,  one  of  the  three  rays  will  be  bent  upward,  even  to  a greater  extent  than  is  repre- 
sented in  fig.  53;  but  these,  it  must  be  recollected,  are  but  accidental  variations  in  form. 
The  shafts  of  the  recurvo-ternate  forms  of  spicula  are  much  less  in  diameter  than  those 
of  the  patento  or  expando-ternate  ones  from  the  same  sponge,  and  they  are  frequently 
very  long  and  exceedingly  attenuated. 
Prehensile  Sjpicula. 
Spicula  projected  from  a sponge  as  a means  of  attachment  to  other  bodies. — I know 
of  hut  one  form  of  this  description  of  spiculum,  an  exceedingly  elongated,  fusiformi- 
acerate  one,  with  a stout  recurvo-quatemate  apex.  It  occurs  at  the  base  of  Euplectella 
aspergillum  and  E.  cucwner,  Owen.  The  long  attenuated  basal  portions  of  the  shaft 
being  -wfithout  spines,  are  incoi-porated  with  the  longitudinal  fasciculi  of  the  skeleton, 
while  the  apical  portions  of  them  are  projected  from  the  base  of  the  sponge,  and 
embrace  and  hook  on  to  any  extraneous  mass  near  which  it  may  be  situated ; and  this 
free  portion  is  thickly  beset  with  strong  acutely  conical  spines,  reflected  at  about  the 
same  angle  and  in  the  same  direction  as  the  radii  of  the  quaternate  apex,  and  to  which 
they  are  auxiliary  as  prehensile  organs ; and  as  we  proceed  from  the  apex  towards  the 
central  portion  of  the  spiculum,  the  spines  successively  decrease  in  length,  until  at  about 
one-third  of  the  length  of  the  spiculum  from  its  apex  they  become  obsolete.  I am 
indebted  to  my  friend  Dr.  Aethue  Faeee  for  the  specimen  figured  of  this  singular  and 
interesting  form  of  spiculum ; and  the  only  sponge  in  which  they  have  been  found  in  a 
perfect  state,  is  the  delicate  and  beautiful  one  designated  by  Professor  Owen  Euplectella 
cucumer.  They  occur  in  great  profusion,  embracing  the  mass  of  matter  at  its  base  in 
every  direction.  I propose,  therefore,  to  designate  this  form  as  an  apically  spined 
recurvo-quatemate  spiculum  (Plate  XXHI.  fig.  53 : a,  the  apical  portion  of  the  spiculum  ; 
h,  a portion  from  that  part  of  the  shaft  at  which  the  spines  become  obsolete). 
As  a solitary  instance  of  the  occurrence  of  a spiculum,  so  singular  in  its  form  and  so 
unusual  in  its  application,  and  being,  like  the  connecting  spicula,  to  a considerable 
extent  incorporated  with  the  skeleton  of  the  sponge,  I have  thought  it  advisable  to 
describe  it  as  an  auxiliary  form,  rather  than  to  consider  it  as  the  type  of  a class. 
