To  arrive  at  a  comprehension  of  their  true  significance  it  is  only  necessary,
however,  to  refer  to  the  life  and  developmental  phenomena  presented  by
the  independent  collared  monads  and  Flagellate  Infusoria  generally.  Here,
both  the  primary  and  terminal  conditions  of  the  typical  flagellate  zooids
are  frequently  characterized  by  the  exhibition  of  a  similar  amoeboid  aspect,
as  is  abundantly  shown  in  the  accounts  and  illustrations  given  of  the  life
and  developmental  phases  of  the  genera  Codosiga,  Salpingosca,  Monas,
OikomonaSj  Euglena^  Eutreptia,  Heteromita^  and  a  host  of  other  forms
described  in  this  volume.  The  capability  of  the  adult  collared  and  flagel-
liferous  spongozoa  to  take  upon  themselves  a  similar  amoebiform  character
has  been  observed  repeatedly  by  the  author,  as  illustrated  in  a  large  number
of  figures  contained  in  PL  VI 1 1.,  which  is  confirmed  by  the  observations  of
Carter,  F.  E.  Schulze,  and  other  recent  investigators,  including  even  Pro-
fessor Haeckel  himself.f  The  amoebiform  elements  of  a  sponge-stock
cannot  therefore  be  consistently  regarded  even  as  independent  structures.
