Page:Proceedings of the Royal Society of London Vol 60.djvu/54

46 ciliated cells proper, and th eir nuclei are larger and paler w ith one or two nucleoli. The nucleus of the first interm ediate cell frequently presents a curious appearance, being swollen out into a large vesicular structure containing two or three chrom atin masses. This condition is apparently in connexion both w ith a process of rearrangem ent of the chrom atin and with the absorption of the vacuoles. The granular cells are arranged in a single layer, and have large pale nuclei w ith nucleoli. Often the nucleus of the cell nearest the interm ediate cells has a pointed outer end, evidently indicating the former connexion with the flagellum.

Sections reveal a rem arkable set of structures in connexion with the central pigment, which is now seen to have the form of a tube, open in front and behind, and enclosing a rounded, lens-like body, apparently a gelatinous mass filling the central cavity, the rem nant, doubtless, of the segmentation cavity. Behind these bodies are a num ber of cells with coarse granules and small, very opaque, deeply staining nuclei.* One of these cells is placed in the longitudinal axis

the Pseudogastrula stage in the Development of Calcareous Sponges,” ‘ Roy. Soc. Victoria Proc.,’ 1889, pp. 93—101.
 * Of. Dendy’s account of the larva of Orantia laiyrinthica for similar cells, “ On