JJ 



J» 



THE president's ADDRESS. 245 



Fig. 3. Slightly later stage, showing commencement of sub- 

 sidiary thickening in the middle of the upper ring 

 of formative cells; sh. sheath, x 1,900. 

 ,, 4. Later stage, showing commencement of manubrium (mn.), 

 formation of silica pockets by the formative cells, 

 and accessory silicoblast {a.s.). x 1,900. 



5. Slightly later stage, with two distinct rings of silica 

 pockets {s.'p.). X 1,900. 



6. Later stage, with the median (m.w.) and subsidiary 



whorl {s.w.) represented each by three solid, conical 

 projections. X 1,050. 

 ,, 7. Fully developed or nearly fully developed spicule, lying 

 in the mesogloea, with accessory silicoblast and 

 other cells ; a.w. apical whorl, other lettering as 

 before, x 1,050. 



Figs. 8-24. LatruncuUa apicalis Kidley and Dendy. 



„ 8. Protorhabd. X 1,050. 



,, 9. Young spicule with basal (manubrium, mn.) and 

 apical (a.tv.) but no median thickening, x 1,050. 

 Figs. 10-13. Young spicules with basal, apical and median 

 thickenings (figs. 9-12 also show commencement, of 

 apical growth), x 1,050. 

 Fig. 14. Stage with well-developed basal and apical thicken- 

 ings and median whorl of three knobs (two only 

 visible) ; also showing the sheath (sh.) and an 

 accessory silicoblast (a.s.). The apical prolonga- 

 tion has been broken short, x 1,780. 



,, 15. Stage in which the median (m.w.) and subsidiary 

 whorl {s.w.) are each represented by (probably) 

 three knobs of silica, which appear to have been 

 formed in silica pockets of the sheath (sh.). The 

 median whorl is displaced towards the manubrium 

 (mn.). An accessory silicoblast is present (a.s.). 

 X 1,780. 



,, 16. Young spicule showing very clearly the apical growth 

 of the protorhabd (pr.), which projects freely beyond 

 the limit of the silica deposit and is also visible as an 



