1106 
DE. J. S. BOWBEBANK ON THE ANATOMY 
ture. The pores, in number, size, and mode of distribution, are very similar to those of 
Polymastia robiista, Bowerbank ; but the stratum of these reticulated skeleton-structures 
is not so thick in proportion, and in Alcyoncellum and Polymastia there is no central 
axial column. I could not detect interstitial membranes in any part of the space inter- 
vening- between the axial column and the dermis in C. jpenidllus', but the skeleton-column 
is permeated by numerous interstitial canals. 
The structure of the short pedicels passing from the axial column to the inner surface 
of the dermis is different from that of the axis ; the spicula composing them are parallel 
to each other, and they are firmly packed together. The bases of the pedicels arise 
from the surface and from within the substance of the central column, with which they 
appear to have no further connexion than that which is necessary to secure them firmly 
in their respective positions. Their apices present a very beautiful appearance, spread- 
ing out towards the inner surface of the dermis in curves diverging at angles of about 
45 degrees in every direction over it, — which, when viewed with a microscopic power of 
about 100 linear, resembles an elaborate and beautifully groined roof of a Gothic crypt. 
Plate LXXIII. figs. 4 & 5. 
Tethea, Lamarck. 
The following are the generic characters given by Lamarck, in his ‘Anim. sans Vert.’ 
2nd edit. ii. 384 : — 
“Tethie {Tethea). 
“ Polypier tubereux, subglobuleux, tres fibreux interieurement ; a fibres subfasciculees, 
divergentes ou rayonnantes de I’interieur a la circonference et agglutinees entre 
elles par un peu de pulpe ; a cellules dans un encroutement cortical quelquefois 
caduc. Les oscules rarement perceptibles.” 
Dr. Johnston’s version of the generic characters differs slightly from Lamarck’s. 
It is as follows : — 
‘‘ Sponge tuberous, suborbicular, solid and compact, invested with a distinct rind or 
skin, the interior sarcoid loaded with crystalline spicula collected into bundles and 
radiating from a more compact nucleus to the circumference. Marine.” 
It is much easier to find faults in the generic characters of both the authors quoted, 
than it is to improve them. The extreme simplicity of the structural characters of 
Tethea is a strong temptation to endeavour to multiply them ; but in doing so. Dr. 
Johnston has introduced two — the structure of the dermal portion of the sponges, and 
the tuberous nature of its surface — which are not common to all the known species. If 
we consider the word “ tuberous ” in the usual English acceptation of the word, as a 
body “ full of knobs or swellings,” then very few or perhaps none of the species of 
Tethea would, in their natural condition, exhibit this character ; but all of them would 
be in a greater or less degree subglobular. Dr. Johnston’s description of Tethea was 
founded on the structure of T. Lyncurium only ; and in this species the “ thick rind ” is 
