Many Physiologists consider that each polype of a P° 
dom, is a distinct being, and consequently that each polyph' 0 ^ 
is a congeries of animals united by a common axis. Tbo«e> 
it is not of much importance whether we deem this opin' 0 
right or not, vet it will be best to consider tbe whole as ° 
compound being, and the polypes as so many mouths thrOUs 
which tbe nutrition is taken in. There is nothing m0r . 
visionary in this multiplication of mouths, than in the n"' 1 
plication of feet in worms. The number of polypes ° n 
polypidom varies according to the species, age, luxuriao 
and innumerable other circumstances; but sometimes ' j 
number is so great as to fill tbe mind with astonishment, aD ^ 
the wonder is increased the more we consider it. In a sp e 
ciinen of Sertutaria argentea of luxuriant growth, in 1,1 
possession, eighteen inches high, there are five pinnae 
whorl, about fourteen whirls in an inch, and about th'f ? 
cells on each pinna, making the polypidom to contain 1 : j 
enormous number of 37800 individual polypes in the space 
a loot and half. 
There is hut little community of feeling existing betwef 1 
the different polypes of the polypidom; tior can it, I tb'° ’ 
he expected from the nature of their internal structo' 
No nervous system has yet been discovered, and from 
simplicity of their organization, no such discovery, is li» e 
to take place. An impression to be felt by more tb 
one polype, must be somewhat roughly communicated, si" 
it is probable, that impressions are communicated chiefly ^ 
the contact of the granules. 
It is generally allowed, however, that there is a coratti" 11 ^ 
of nourishment, and no one, who has watched these anin' 0 ^ 
will call it iu question. If a Sertularia be taken, and 0 j 
only of its polypes be fed, nourishment is evidently supp* 
to all the rest and to the central palp, which according j, 
Grant * is furnished with a central canal, through w 
tbe nutrient matter is conveyed. The lentaenla like 
body, are contractile in every part, and are tuberculated; 
tubercles being circularly arranged. Grant is evidently, 
error when be says that tbe tenlacula are ciliated, for a \ jj 
many microscopic examinations on the majority of the Cor ' 1 ' i 
species, I have never detected cilia in a single instnnce> a . 0 
Dr. Johnston, a good authority, is of the same opinion. 
mouth is also capable of a great deal of elongation and ° t 
traction, sometimes being conoidal and at others flat; so 
at different times the polypes present a great diversity ol *° 
Outlines of Comp. Anat., p, 13. 
