22  The  Florida  Sponge  Industry.       { re- 
consider how  they  are  formed  ;  that  is,  whether  they  are  plants  or 
animals,  or  what  their  history  or  habits  may  have  been. 
Sponges  consist  of  a  framework  or  skeleton,  coated  with  gelati- 
nous matter  and  forming  a  non-irritable  mass,  which  is  connected 
internally  with  canals  of  various  sizes.  The  ova  are  very  numerous, 
and  present  in  appearance  the  form  of  irregular  shaped  granules 
derived  from  the  gelatinous  matter  which  grow  into  ciliated  germs, 
and,  falling  at  maturity  into  small  canals,  are  then  expelled  through 
the  orifices.  When  alive,  the  body  is  covered  by  a  gelatinous  film, 
which,  being  provided  with  cilia,  causes  a  current  of  water  to  pass 
in  at  the  smaller  pores  and  out  at  the  larger  apertures,  the  sponge 
probably  assimilating  the  nutritive  principles  contained  in  the 
water. 
Sponges  are  found  abundantly  in  tropical  waters,  generally. 
They  gradually  decrease  in  numbers  towards  the  colder  latitudes, 
till  they  become  entirely  extinct.  They  vary  much  in  shape. 
Some  are  shaped  like  a  vase,  others  are  semi-cylindrical,  others 
flat  like  an  open  fan,  and  some  are  round. 
The  commerce  in  sponges  is  of  considerable  importance.  The 
great  difficulty  which  is  experienced  in  any  attempt  to  distin- 
guish species,  results  from  the  extreme  susceptibility  of  all  kera- 
tose  sponges  to  any  change  in  external  conditions.  They  appear  to 
require,  for  the  production  of  the  forms  in  abundance,  tropical  or 
sub-tropical  seas,  and  attain  by  far  their  greatest  development  in  the 
number  of  the  forms  and  species  in  the  Gulf  of  Mexico  and  West 
Indian  seas.  The  typical  forms,  the  commercial  sponges,  are  essen- 
tially confined  to  the  waters  of  the  Bahaman  Archipelago,  and  the 
southern  and  western  coasts  of  Florida  in  the  Western  Hemisphere, 
and  to  the  Mediterranean  and  Red  Seas  in  the  other. 
The  Florida  sponge  grounds  form  three  separate  and  elongated 
stretches  along  the  southern  and  western  coasts  of  the  State.  The 
first  includes  nearly  all  of  the  Florida  reefs,  the  second  extends  from 
Anclote  Keys  to  Cedar  Keys,  and  the  third  from  just  north  of  Cedar 
Keys  to  Saint  Mark's.  The  Florida  grounds  have  a  linear  extent 
of  about  1 20  miles,  beginning  at  Key  Biscayne,  in  the  northeast, 
and  ending  in  the  south  at  northwest  channel,  just  west  of  Key 
West.  The  northwestern  half  of  the  grounds  is  very  narrow,  having 
an  average  width  of  only  about  five  miles,  and  being  limited  to  the 
outer  side  of  the  reefs.    At  about  the  Matacumbo  Reefs  the  grounds 
