2: 
POLYZOA. 305 
Respiration is provided for in the Polyzoa by the ciliated append- 
ages which surround the mouth; they are at once tentacula’ and 
branchiz. The animal presents no other trace of organs of the 
special senses. A small ganglion and a few threads constitute all of 
the nervous system which can be traced; neither heart nor blood- 
vessels have been found. 
The egg, in the case of the Polyzoa, gives birth to a young animal 
covered with cilia on its surface ; it swims about freely until it has 
chosen a convenient place in which it can establish the new colony 
which it is to originate. At first, the number of the colony is only 
increased by budding, but in a short time the individual polyps 
produce eggs. 
From these remarks it will be seen that the animals of the Polyzoa 
are more complex in their form and functions than those of the 
Ceelenterata, and the further study of their anatomy confirms this 
conclusion. In their case the digestive organs are no longer a 
simple sac with a single orifice ; there is a mouth, a pharynx, a gullet, 
a gizzard, a membranous stomach and intestines, with a special 
opening for these latter. We have descriptions of some species in 
which the gizzard seems to be provided with a certain number of 
interior teeth, forming a wonderful pavement—a living mill for the 
purpose of grinding the food before it enters into the second stomach. 
The organisation of this small creature reveals to our eyes a wonderful 
amount of combination—of admirable art immeasurably surpassing 
all that the most perfect human industry and human genius could 
accomplish. 
After this general view of the organisation of the group, we shall 
proceed to introduce the reader to some of the more characteristic 
species. 
Under the leaves of water-lilies (Vymphea), pond-weed (Fotamo- 
geton), or upon floating fragments of submerged wood, are generally to 
be found certain Polyzoa, animals described by Trembley under the 
name of plumed polyps. These will probably belong to the genus 
Flumatella (Fig. 120). These little diaphanous creatures constitute 
colonies which under the microscope resemble small branching 
shrubs; they consist of small slender tubes fastened one to the other, 
and having from forty to sixty retractile tentacula, which expand like 
the petals of a flower ; they are furnished with vibratile cilia, the move- 
ments of which serve the purpose of leading food into the mouth. 
Another genus, which is found in ponds in France, and which is 
also found in fresh water in Britain, is the Crstatella of Cuvier. 
“ Perfect specimens of C. mucedo occur from six lines to twenty-four 
U 
