670 PROF. SCHULZE ON THE STRUCTURE AND ARRANGEMENT 
disposal was not sufficient to allow me to gain a clear idea of the nature of the 
epithelium of the ciliated chambers, I was able to observe the following facts. 
I could perceive all the cells in the form of aggregated roundish lumps, in the 
centre of which a small spherical nucleus, furnished with a smaller strongly 
refractive nuclear corpuscle (like that which appears in the collar-cells of 
ether sponges), was sharply defined by means of a tinging medium (Pl. X VIL. 
figs. 6 and 7). If, therefore, nothing was to be observed in my preparations 
of the cylindrical form of the cells, of the peculiar collar-like process, of the 
collar, or of the flagellum which appears in the collar-cells of other sponges, 
it by no means follows that they are wanting in the living animal. The 
fact that in this case the cells of the ciliated chambers do not touch each 
other immediately laterally, but lie apart at nearly equal distances, did not 
surprise me, as I had occasionally found the same in other sponges—for 
example, in Spongelia—in pieces which had not been quite sufficiently 
hardened for examination. On the other hand, the peculiar arrangement 
and lateral connection of the cells with each other seemed to me highly 
remarkable. 
Even under a comparatively low magnifying power we can see a reticulate 
arrangement in the ciliated chambers, which has never yet been described in 
any other sponge. The cells, which are arranged in spiral or oblique rows, 
and lie somewhat apart, are connected in such a way by tolerably strong re- 
fractive straight cords, that rhomboidal quadrate meshes are formed which are 
usually of nearly equal size, and only here and there become varied in form and 
arrangement by the pores of the chambers. While usually four such lateral 
connecting cords, forming a straight or oblique cross, proceed to the adjacent 
cells, there are not rarely five or six such processes. I could not find any 
complete explanation of the nature of these connecting cords and their relation 
to the cells; but I believe we must consider them as connecting bridges 
between the viscid cell bodies. 
The Mesoderm.—In contrast to most other siliceous sponges, the scanty 
gelatinous connective tissue of the mesoderm has a semi-fluid colourless funda- 
ment basis, hyaline in itself, but rendered turbid by numerous irregularly 
scattered fine darker particles. The sort of difference which we have in many 
horny and ‘siliceous sponges, between the equally dark granuled boundary of 
the ciliated chambers and the rest of the hyaline masses of connective tissue, is 
not to be observed here, Besides the small round nuclei of the outer epithelium, 
more faintly defined and usually oval-shaped nuclei, at whose narrow end 
we often find a still smaller nuclear mass, may be observed in the cribriform 
layer, as well as in the flat plates and cords of the remaining soft parts. 
I have, therefore, less hesitation in referring these pale oblong nuclei to 
