ZOOPHYTA ASTEROIDA. 
165 
In every polypidom of this order there are three parts which 
require notice, — the polypes, the fibro-fleshy calcareous crust 
in which they are placed, and the internal axis. The con- 
nection between these parts is indissoluble, and although 
we may treat of them separately, and as if they were some- 
what independent, yet we must guard against the entertain- 
ment of any such opinion. # It was once indeed a debated 
question whether each polypidom might not rightly be con- 
sidered a mere aggregation of separate animalcules, but all that 
we know of their habits and structure goes to prove the contrary, 
so that no one probably now disputes that the polypidom with 
its polypes constitute but one body, the latter being in the place 
of as many mouths and stomachs scattered over the surface. 
The whole mass, with the exception at most of the axis in those 
which possess a stony or horny one, is living and organized, re- 
ceiving the material of its nourishment and growth from the food 
captured and digested by the polypes ; and as they have not 
only an organical union with the irritable flesh in which they are 
immersed, but are many of them more intimately associated to- 
gether by means of canals and intestines, so they participate in 
every benefit and every evil. When, therefore, one pinna of a 
Sea-Pen is lacerated or cut away, the remaining pinnae gradu- 
ally shrink, the polypes withdraw, and the whole body con- 
tracts in every dimension ; or if a portion of the Alcyonium be 
subjected to irritation, the gradual collapse and contraction of 
the polypidom renders it obvious that the irritation has been 
communicated and felt through the entire mass.f On the con- 
ed by the providence of nature, for that the edges of them do in that posture 
with most ease cut the water flowing to and fro ; and should the flat side be ob- 
jected to the stream, it would soon be turned edge-wise by the force of it, be- 
cause in that site it doth least resist the motion of the water : whereas did the 
branches of these plants grow round, they would be thrown backward and for- 
ward every tide. Nay, not only the herbaceous and woody submarine plants, 
but also the lithophyta themselves affect this manner of growing, as I have ob- 
served in various kinds of corals and pori.” — The Wisdom of God in the Crea- 
tion, p. 77. 
* Tiedemann has inadvertently asserted that the polypes “ are able to leave 
the crust and return to it.” Comp. Phy. 306. 
•j- “ Unknown to sex the pregnant oyster swells, 
And coral-insects build their radiate cells ; 
Parturient Sires caress their infant train, 
And heaven-born Storge weaves the social chain ; 
