Am.  Jour.  Pharm. 
■  April,  1881. 
185 
Nodular  flints  are  believed  to  be  fossil  sponges,  as  are  also  the  celebrated 
*'moss  agates."  Fossil  sponges  of  many  species  are  found  in  many  locali- 
ties in  this  country,  notably  in  Kentucky  and  Tennessee.  Spicules  pre- 
dominate so  far  in  some  sponges  as  to  render  them  valueless,  and  their 
.a,bsence  is  always  essential  to  its  domestic  uses. 
The  sponge  is  propagated  by  an  ovum  or  germicule  cast  from  the  parent 
-at  certain  seasons,  this  being  usually  a  ciliated  cell,  w^hich,  floating  for 
avi^hile,  at  last  settles  for  life  on  some  hard  substance,  and,  giving  no  signs 
of  sensibility,  yet  undergoes  a  change,  the  gelatinous  flesh  is  riddled  and 
channeled,  the  fibrous  framework  is  formed,  and  the  sponge  is  complete. 
The  process  of  generation  is  involved  in  some  doubt,  but  they  seem  to 
contain  witliin  themselves  the  power,  and  seemingly  by  germination  or 
budding.  These  germicules  are  apparently  produced  in  some  of  the  cells, 
and  pass  through  the  sarcode  to  the  large  canals,  from  which  they  are 
•ejected,  sometimes  being  protected  and  surrounded  at  their  exit  by  spicules. 
The  duration  of  life  and  rapidity  of  growth  are  not  known,  though  in  the 
Mediterranean  it  is  agreed  that  tlie  ground  may  be  fished  over  again  in 
three  years.  The  period  probably  varies  greatly  in  different  latitudes,  for 
the  species  are  widely  distributed  over  the  seas;  they  are  scarce  and  small 
in  cold  latitudes,  and  increase  most  abundantly  in  the  tropics. 
Many  strange  and  beautiful  forms  occur  among  sponges,  some  of  which 
have  received  popular  names,  as  Feather,  Fan,  Bell,  Lyre,  Trumpet,  Di- 
staff, Peacock  Tail,  Neptune's  Glove,  Neptune's  Car,  Venus'  Flower-basket, 
Glass  Sponges,  etc. 
The  cornucopia-shaped  Glass  sponge,  the  Venus'  Flower-basket  {Euplee- 
tella  speciosa — the  specially  beautiful  well-woven),  is  one  of  the  rarest,  and, 
as  its  name  implies,  one  of  the  most  beautiful  varieties.  It  is  found  near 
the  Philippine  Islands.  It  resembles  a  structure  of  spun  glass,  and  though 
apparently  so  delicate  is  yet  quite  strong;  each  thread,  although  of  pure 
silex  and  seemingly  solid,  is  really  composed  of  a  series  of  concentric  tubes 
or  cylinders,  as  if  spun  on  a  central  thread.    As  the  threads  are  of  pure 
Fig.  8.— 
Spicules  of  various  forms. 
