160 
ZOOPHYTA ASTEROIDA. 
trary, when at rest and undisturbed, the polypes protrude their 
tentacula and a portion of the body, and, imbibing the circum- 
fluent water, this percolates into the interior through numerous 
anastomosing canals, and distends the polypidom so much that 
it will more than double or treble its former size. In this re- 
spect the Zoophyta asteroida show an affinity to the Helianthoida, 
and differ from the hydraform and more especially from the as- 
cidian orders. 
The axis of the Alcyonidae is imperfect, but exists neverthe- 
less in the form of calcareous or siliceous spicula diffused through 
the gelatinous interior, or more or less densely clustered at the 
centre ; and the appearance of these spicula is such that we 
are almost tempted to believe they may possibly be the products 
of crystallization rather than of any regular secretion.* It might 
not be difficult, but it is beyond my province, to trace the gra- 
dual increase and consolidation of these spicula through many 
intermediate species to the horny flexible axis of Gorgonia, 
where it has become such an efficient support to the whole soft 
envelope as to claim not improperly the name of its skeleton ; 
thence to the stony axis of the coral ; and having there reached 
its maximum of developement, I might, on the other hand, have 
marked its progress towards degeneration until it became again 
only a partial support, such as we find it in the naked middle 
portion of the Pennatulidse, more especially in some of the fo- 
reign and less typical species of that family. 
According to Lamarck, this axis, under all its modifications, is 
inorganic, containing neither vessels nor any portion of the 
body of the polypes, but formed of matter excreted by them, 
and afterwards thickened, solidified and depurated by af- 
finity. -f Although this is rather, on Lamarck’s part, the de*- 
Successive births her tender cares combine, 
And soft affections live along the line.” 
Darwin’s Temp, of Nature, canto ii. 
* They may be compared with the JRaphides found in the intercellular pas- 
sages of certain monocotyledonous plants. See Lindley’s Introd. to Botany, 
p. 29 Mr Children found in the ashes of a piece of the axis of Gorgonia 
Flabellum, a distinct trace of pure silica, sufficient to form a globule before the 
blow-pipe Ann. of Philosophy, New Series, Vol. ix. p. 431. 
t “ L’observation constate que 1’axe central de ces polypiers, quoiqu’ offrant 
quelquefois des couches concentriques, ne fut jamais organise, n’a contenu ni 
vaisseaux quelconques, ni aucune portion du corps des polypes ; qu’il est le 
resultat de matieres excretees par ces polypes, matieres qui se sont epaissies. 
