SEA-ANEMONES. 
5°3 
single individuals from eggs, some multiply by the detachment of small pieces from 
the pedal disc. Fischer observed this process in the translucent anemone (Sagartia 
pellucida ) on the French coast. The pieces detached 
on the 23rd of August had, by the 7th of September, 
developed into small individuals with fifteen or 
sixteen tentacles. Multiplication by fission seems 
common in several species, such as S. ignea, and 
always ends in producing single individuals. Sea- 
anemones sometimes, however, form stocks, but are 
then no longer called Actinia but Zoantharia. Such 
stocks are not very numerous, but some species can 
be found on European coasts. The genus Zoan- 
tharia, in which the separate individuals are united 
by a creeping branching root, is distinguished from 
Palythoa, in which the common stock resembles a 
root-like crust, on which the polyps form irregular 
groups of various sizes. A peculiarity common to 
the two genera is the incorporation of hard particles 
of the most different kinds—sand, sponge-spicules, 
pieces of shell or coral—into the body-wall in large 
quantities. The walls in consequence become so firm 
that the exact form of the polyp is retained in dried 
specimens. The species of Palythoa, although un¬ 
attractive when in spirit, are of a sulphur yellow, 
and beautiful when alive in an extended condition. 
The most interesting species is Palythoa fatua, 
which is always found growing on and in one of 
the most curious of sponges, the Japanese glass- 
sponge ( Hyalonema ). Here the surface of the stalk, 
that is above the portion embedded in the mud, is 
covered with a warty crust belonging to this 
Palythoa. All the specimens of this Japanese 
sponge in European museums in 1860 had their 
stalks overgrown with the Palythoa, while many 
had their bodies also covered with another polyp 
which, however, settled singly and, fortunately for 
the sponge, did not form a sandy crust. The illustra¬ 
tion represents a specimen of this beautiful glass 
rope-sponge, its body pitted all over with holes in 
which small Anthozoa once lived, and its stalk 
coated with the sandy crust of the stock-forming 
Palythoa. The former, having no skeleton, dry up 
entirely; no traces of them being found in dried 
specimens of the sponge except the holes they lived in. Unlike a parasite, the 
polyps do not feed upon the juices and soft-parts of the sponge, nor indeed do 
they share its food, but simply settle upon the sponge and feed upon the food that 
parasitic anemone ( Palythoa ) ON 
STALK OF GLASS - ROPE SPONGE 
(J nat. size). 
The holes on the body of the sponge 
are formed by antliozoans. 
