18 GEORGE BIDDER. 
possessed a globule containing angular dark particles,—some- 
times, as in fig. 4, projecting on the surface between collar and 
flagellum. These globules were observed and drawn moving 
in the distal protoplasm of the cells; there were numerous 
bodies of similar appearance (cf. fig. 13a@) floating freely in 
the chamber. It is possible that they were some minute 
organism with whose appearance I am not acquainted; but 
the strong suggestion was that they were ejecta. I have often 
suspected, from paraffin sections, that the food vacuoles of 
sponges are filled with some gelatinous matter, coagulated in 
preservation. 
The “vacuoles” in fig. 5 and fig. 9 were also moving in 
the protoplasm, but it does not seem impossible that they 
were nuclei (a view established since this was in type). 
In paraffin sections stained with hematoxylin the free end of 
the cell very noticeably appears, with the ordinary immersion 
lens, as a dark band (figs. 15, 17, 18). Viewed from above, it 
is often seen that this stained area is really annular (cf. cut, d), 
the flagellum appearing as the dark centre of a white disc, which 
is generally about one third the radius of the intra-choanal area. 
And with the apochromatic immersion it can be seen in profile 
to be indeed the case that at the focus of the flagellum the 
terminal plate of stained matter is interrupted by an unstained 
interval, showing that the substance stained is arranged as a 
diaphragm, and not a complete disc (cf. cut, d). In the profile 
of cells treated with acid alcohol after staining, the hematoxylin 
is found to be confined to this diaphragm, the protoplasm be- 
neath being comparatively unstained. 
In many of the cells viewed from above the stained annulus 
shows a radial structure. Though marked in a few cases, in 
most cells it is impossible with the magnifying power employed 
to make certain whether this exists or not; but generally in 
the optical profile the dark line marking the section of the 
annulus is to some extent beaded, or broken, especially on 
focussing above or below the flagellum. Where the rays were 
recognised, their number was never more than ten or twelve 
(cf. cut, d) ; on the other hand, the root of the collar, focussed on 
