OF POLYPES. 
39 
connection with it. They, as already mentioned, are found 
lodged in a sort of Fig . 5. 
cell (Fig. 5. a.) exca- 
vated in a sarcoid crust, 
which constitutes the 
main bulk of the po- 
lypiferous mass, and 
which, in fact, is no- 
thing more than a mo- 
dification of the bases 
and outer skin of the 
polypes hardened by a 
deposition of calcareous 
granules and spicula, 
and made more coria- 
ceous in texture, to 
bear with impunityYhe 
contact and ruffling of 
the water.* This crust is accordingly a living irritable struc- 
ture, permeated by tubes prolonged from the polypes and by 
capillary canals, for the conveyance of water and nutriment to 
every part. 
The connection between the crust and the polypes is there- 
fore of the most intimate kind, and if for conveniency the latter 
are separately described, the reader should ever remember, that 
this separation is a forced and artificial one. An asteroid po- 
lype mass is known by the orifices of the cells forming on the sur- 
face a mark more or less resembling a star, as commonly repre- 
sented in maps — hence the name of the order: when the polype is 
* “ Lorsqu’on observe les Alcyons dans leur etat naturel, la ligne de demarca- 
tion entre ces deux parties parait bien trancbee, et on pouvrait au premier abord, 
croire ces petits animaux loges dans des cellules au pourtour de l’ouverture des- 
quelles ils adhereraient ; mais quand on eleve a l’aide d’un acide etendu d’eau, 
le depot calcaire dont la base du polype est environee, on voit qu’il y a entre 
ces parties continuity organique, et que la cellule polypifere n’est autre chose 
que la portion inferieure du corps du polype qui, en se contractant, rentre en 
luimeme, comme nous 1’avons deja vu pour les Alcyonides. Le polypier com- 
mun n’est en effet autre chose que la resultat de l’aggregation intime de la por- 
tion basilaire des polypes.” Milne- Edwards in Ann. des Sc. Nat. iv. 336. an 
1835. The student may compare this with Lamouroux’s description of the Gor- 
gonia. Corallina, p. 198. 
