ON THE SKELETONS OF ZOOPHYTES* 
179 
the minute Polypi. The transition from Corallidce with a horny to those with a 
Calcareous axis is observed in the interesting genus Isis. In this zoophyte the 
internal organ of support presents an articulated character, from the alternate 
segments of the stem and branches being composed of horny and Calcareous 
matter, in cabinet specimens the dessication of the former gives the skeleton a 
jointed air. This beautiful provision, which gives a greater range of movements 
to the zoophyte, and by admitting of extensive flexion in the stem and branches 
diminishes its liabilities to fracture from the violence of the waves, is secured 
simply by an arrest of the process of Calcification at definite intervals ; or, in 
other words, the horny parts are uncalcified portions of the general solid axis, and 
are analogous in their structure and development to the skeletons of Gorgonia 
and Antipathes. The study of Isis conducts us naturally to Corticiferd , with a 
Calcareous skeleton, as in the common Red Coral (Corrallium rubrum). This 
arborescent Polypifer is attached by an extended base to submarine bodies, and 
grows to about a foot in height, the red-coloured stem is invested by a fleshy 
crust, in the thickness of which the numerous Polypi that crowd its surface find 
a secure retreat* These sensitive digestive sacs are furnished with eight foliaceous 
tentacula, which are seen busily extended in search of prey. The Calcareous 
skeleton resembles a miniature tree denuded of its foliage, is of a bright vermillion 
tint, and so dense in texture that it is suscepible of the highest polish* The 
colour of the Red Coral varies considerably in the intensity and beauty of its dye* 
according to the depth of water in which it is developed, the colouration depend^ 
ing on the influence of light; it is for this reason that molluscs and zoophytes 
inhabiting the oceanic bed at considerable depths from the surface are deprived of 
the delicate and vivid hues that adorn other species of the same genus, placed 
by the nature of their habits and instincts within the more immediate influence 
of the solar rays. The Pennatulidcs are so called from their general resemblance 
to a feather. The body is fleshy, more or less cylindrical, and supports an oval¬ 
shaped head composed of numerous diverging arms, which have a similar situation 
and direction to the barbs that spring from the shaft of a feather j each ray arises 
from the central stem by a distinct root, and supports upon its upper surface 
numerous cells for lodging the Polypi. These processes increase with the age of 
the animal; in the specimen before me I can count thirty rays on each side of 
the stem. They are free, and eminently phosphorescent zoophytes, and swim 
through the ocean by the movements of their celluliferous arms. This fact I am 
enabled to state, in contradiction to an opposite opinion maintained by many 
modern zoologists, from observations made on a fine specimen of Sea-pen ( Penna- 
tula phosphorea) four inches in length, captured by my wife, on the Scottish 
coast. This lady, to whose acute observations on natural phenomena I am 
indebted for many valuable facts, had the good fortune to place the specimen, 
YOL. IV.-NO. XXVIII* 2 B 
