MATERIALS FOR -A MONOGRAPH OF THE ASCONS. 30905 
Figs. 90—100.—Development of the triradiate and quadriradiate 
systems. 
Figs. 90, 91.—Sextetts. In Fig. 91 the small size of the nuclei indicates 
recent origin by division from the three actinoblasts. 
Fies. 92—95.—Four young quadriradiates, drawn from the dermal side; 
the spicules are slightly corroded by the glycerine. On each ray are seen the 
two formative cells, basal “thickener,” and apical “founder.” The gastral 
actinoblasts, being under the spicules, are not clearly seen, but can be made 
out to contain each a single nucleus. In Fig. 94 two cells of the overlying 
dermal epithelium (d.ep.) are drawn. 
Fics. 96—100.—Rays of triradiate and quadriradiate systems, showing the 
migration of the ‘thickener ” to the apex of the ray and the disappearance 
of the “founder.” Figs. 98 and 100 are full-grown spicules, having the 
thickeners on the extreme points of the rays. 
Fie. 101.—Abnormal triradiate of Clathrina coriacea. X 1250 linear. 
One of the rays has branched into two, each branch bearing a scleroblast. 
Fics. 102, 103.—Amcebe found commonly on the exterior of Leucoso- 
lenia variabilis. x 1000 linear. 
PLATE 21. 
Spicules, etc., of Leucosolenia lieberkithnii from Naples. 
Figs. 104—107, natural size. Figs. 1O8—122, x 170 linear. 
Fies. 104—107.—Specimens of the sponge. Fig, 107 shows an unusually 
large oscular tube. 
Fie. 108.—Distal end of a diverticulum ; on the surface only the triradiate 
systems and pores are drawn; at the edge, in optical section, only the 
monaxons are shown. 
Fics. 109—112.—Triradiates, isolated. 
Fies. 113, 114.—Quadriradiates. 
Fies. 115—119.—Ordinary monaxons. 
Figs. 120—122.—“ Walking-stick”? monaxons. In Fig. 122 the distal 
extremity is shown more highly magnified. 
