1092 
DE. J. S. BOWERBANK ON THE ANATOMT 
that is exhibited in Grantia compressa and the allied species, and we observe a pro- 
gressive decline in regularity of structure in its genera very analogous to what we 
find existing among the Halichondroid tribe of sponges ; but in this respect they only 
follow the same laws of gradual degradation that obtain in every other class of created 
beings ; and therefore this gradual decline in regularity of structure should not militate 
against the claim of even the lowest in organization of the tribe from taking precedence 
of the siliceous sponges. 
Dr. Geant was the first naturalist who decided that the spicula of a certain group of 
small sponges were composed of carbonate of lime, and he separated them accordingly 
from those the spicula of which were siliceous, and assigned to them the generic name of 
Leucalia (Edinburgh Encyclopaedia, vol. xviii. p. 844) ; and subsequently, in his ‘ Outlines 
of Comparative Anatomy,’ he changed that name to Leuconia. In 1828 Dr. Fleming 
gave to the group the name of Grantia^ in compliment to the learned naturalist who 
had first pointed out their peculiar structure. 
A careful examination of the British species of this Order will very soon satisfy a 
naturalist that there are at least four distinct forms in the organization of the skeleton, 
and that each is fully entitled to generic distinction. Thus in Grantia ciliata and 
compressa, Johnston, we find the sponge to be constructed of a series of cells, each 
having separate parietes, and extending from the dermal surface to near the inner 
surface of the sponge, where they discharge the fsecal streams into a common cloacal 
cavity. In Grantia hotryoides, Johnston, the system of cells is entirely wanting ; the 
sponge is composed of a single thin stratum of membranous structure and spicula, 
surrounding a large cylindrical cloacal cavity, from the terminations of which the fsecal 
streams are discharged. In Grantia nivea, Johnston, we find the sponge massive and 
hregular in form, containing numerous capacious cloacal cavities, each terminated by 
a single large mouth, the interstitial structures between the sides of these great cavities 
and the dermal surfaces of the sponge consisting of irregularly disposed membranes and 
spicula, permeated by contorted interstitial cavities, terminating in simple orifices or 
oscula in the sides of the great fsecal cavity into which they discharge their excurrent 
streams; and in Leucogyjysia Gossei, Bowerbank, MS., the sponge is massive, without 
cloaca, formed of irregularly disposed membranous tissues and spicula, and with oscula 
at the external surface, thus simulating to a great extent the mode of structure of the 
TIalichondroid tribes of sponges. 
The sponges of this Order appear to possess a high degree of vital power, and I have 
rarely failed in finding the excurrent orifices in vigorous action in either 6rrantia com- 
jpressa, ciliata^ or hotryoides when recently taken from the sea. In G. com/pressa, espe- 
cially, I have often observed the inhalant and exhalant actions remarkably vigorous ; and 
if a drop of water containing finely comminuted indigo be mixed with the water in which 
they are immersed, they will become deeply tinctured with it in a very few seconds. 
This vigorous action is accounted for by the highly developed ciliary system, which may 
-be readily seen in action if the sponge be carefully split open and immersed in fresh cold 
