304 
POPULAR SCIENCE REVIEW. 
and at all other periods of the year ; and that this species is 
perennial is rendered probable by the fact that the statoblasts 
are very sparingly produced when compared with the im- 
mense profusion yielded by other kinds. The attached forms 
of the Fresh- water Polyzoa are readily found, if the collector 
will patiently examine submerged branches of trees, or the 
under-side of leaves and stones ; for the large sponge-like 
masses of Alcyonella, the branching tubes of Plumatella, and 
the tangled interlacements of Fredericella are apparent to the 
eye without an effort — though at the same time, perhaps, if he 
had never seen a single specimen, he would either not notice 
them or would fail to discern in them objects of much interest. 
The Polyzoa afford a most instructive example of the neces- 
sity to pay particular attention to the internal structure and 
anatomy of any animal, if we would desire to ascertain its 
place in the animal kingdom. In external form the members 
of this group bear a very close resemblance to pliytoid Zoophytes 
with which indeed they were long confounded. Now these latter 
animals belong to the low-organized class known by the name 
of Hydrozoa, of which the common Hydra or Fresh-water 
Polype, may be taken as the type. But the Polyzoa, notwith- 
standing their resemblance to, are widely separated from this 
group, and represent in their structure analogies with that sec- 
tion of the molluscan sub-lciugdom happily designated by Milne 
Edwards Molluscoida. “You go down,” says Mr. Kingsley, 
“ to any shore after a gale of -wind, and pick up a few delicate 
sea-ferns. You have two in your hand ( Sertularia operculata 
and Gemellaria loriculata), which probably look to you, under 
a good pocket magnifier, identical, or nearly so. But you are 
told, to your surprise, that however like the dead horny poly- 
pidoms which you hold may be, the two species of animals 
which have formed them are at least as far apart in the scale of 
creation as a quadruped is from a fish.”* The Polyzoa have now 
been admitted to their proper place in the animal kingdom, 
and have been advanced from the sub-kingdom Radiata (now 
Ccelenterata) to that of the Mollusca. “ Thus,” as Dr. Car- 
penter instructively remarks, “ whilst microscopic research has 
degraded the Foraminifera from their supposed rank "with the 
nautilus and cuttle-fish to the level of the sponge, it has raised 
the wheel-animalcules into proximity with aquatic worms and 
the humble ‘ sea-mat ’ (flustra), formerly supposed to be a 
plant, to a position not much below that of the oyster and 
mussel.” f 
The Polyzoa having an organization homologous with the 
* Glaucus, p. 33. 
t “ The Microscope and Its Revelations,” p. 18, 2nd ed. 
