686 K. KIKKPA'L'lUCIv. 



spot, about 2 mm. in diameter, on the inner surface of a shell. 

 The figure (PI. 32, fig. 12), magnified twenty-five times 

 linear, shows the delicate polygonal network below the surface 

 of the sponge. There are no crypts at tliis stage, but simply 

 the slender strands or bars of the wide-meshed network, 

 with small tubercles at the nodes. 



A vertical decalcified section, highly magnified (PI. 38, 

 figs. 1-3), shows a layer of cells all over the sponge at, or 

 rather just below, the surface. The cells have processes 

 which branch dendritically into innumerable slender fibrillee 

 or filaments. Thefibrillfe passing to the surface form a thin, 

 surface feltwork, which shows as a thin line in the section. 



Bundles of fibrillee pass down from the cells of the upper 

 surface, and up from the basal cells. Occasionally the opposing 

 filaments meet and almost form a central, horizontal lamina, 

 especially near the periphery of the sponge, Avhere the upper 

 and lower surfaces are very close together. The waving 

 masses of branched fibrils almost resemble the flames of a 

 conflagration as conventionally depicted. 



The calcocytes are elongated, and mostly congregated near 

 the base of the crust and orientated at right angles to the 

 base, like a field of stakes or hop-poles. Many of these cells 

 are embraced between bundles of fibrillte passing up from the 

 basal branched cells. 



The flagellated chambers are not yet formed, but the collar- 

 cells are present as small wedge-shaped cells which here and 

 there show a tendency to be arranged in half circles (as seen 

 in section). Further, some Avedged-shaped cells appear to be 

 prolonged at their acute angle into a filament which joins on 

 to a main filament, like the main stalk and secondary stalks 

 of a pinnatifid leaf. Apparently the main stem and lateral 

 stems represent the beginnings of the canal system. I have 

 not been able to determine the nature and relations of these 

 bnmched filaments; possibly they are the processes of con- 

 nective-tissue cells. 



Scleroblasts and their spicules are abundantly present. 



The little grooves or arches at the base of the section are- 



