8 R. KIEKPATEICK. 



mind the species of Fangophilina Schmidt, viz. F. submersa 0. Sch. (17. p. 73), and 

 F. gilchristi Kirkp. (10. p. 667), in which the ovoidal body of the sponge has' one 

 large porocalyx and one large oscule situated on the upper aspect. As the sponge 

 grows, the porocalyces increase in number and extend on each side of the original one 

 till they form a complete equatorial belt ; in the meantime, the main axis of the sponge 

 gradually rotates from horizontal to vertical, so that the crown of oscules comes in 

 many specimens to lie in a horizontal plane at right angles to the vertical axis. 



The cortex. In young specimens the cortical oxeas are arranged tangentially 

 in a single layer. In the largest examples, the cortex reaches a thickness of 3 "25 mm., 

 the densely packed oxeas being arranged vertically and obliquely to the surface. 



The skeleton. The only additional observations to be made here are on certain 

 bodies which SoUas (21. p. 24) refers to as " Globules ; accessory or accidental forms, 

 0*0535 mm. in diameter." These bodies, which Schulze terms "silica pearls," are now 

 known to be not uncommon in sponges (Schulze, 18. p. 6, and Weltner, 33. p. 190). 

 Spheres may be normal spicules of the sponge, as in Caminus sphaeroconia SoUas. In 

 many instances, however, spheres or globules result from malformation or incomplete 

 development, as in cases where a tylote spicule is reduced to a knob, or a sphere may 

 result from the reduction of an oxea, as in Epallax callocyathus SoUas. In some of 

 the specimens of C. barhata there are a considerable number of pearls and some of them 

 are double (IX. 6, 7). One example 114 x 94 /x is oval, with two nuclei and with 

 concentric layers of deposition round each, up to the point where the spheres come in 

 contact ; later there is a single oval layer common to the two centres, but an annular 

 depression or kink is always visible in the plane midway between the nuclei of the two 

 original spheres. SoUas (21. p. 214, PI. XXVIL, figs. 8-9) figures composite spheres 

 occurring in Caminus sphaeroconia, but here the composite sphere does not possess 

 separate central points round which are deposited concentric laminae, but (apparently) 

 one centre and an axial line or rod round the end of which the layers are deposited. 



Whether these spheres or silica pearls are always spicules or the result of incom- 

 plete development of spicules, or whether they are sometimes due to deposition of 

 layers of silex round some foreign organic or inorganic body, has not been determined. 

 The nucleus is generally a refringent point, but is sometimes irregularly shaped and 

 of a faint yellow colour ; attempts to investigate it under high powers generally result 

 in the pearl being crushed. 



Several of the smallest pearls, only 6 or 7 ju in diameter, are associated with fan- 

 shaped crystalline bodies (IX. 8-12) ; these latter proved to be simply crystals 

 deposited from the sea-water. Sometimes the pearl is in the centre of a spheroidal 

 mass of crystals. Under polarised light, the crystals are doubly refracting and are 

 brilliantly defined on the dark field, while the pearls are isotropic, though usually very 

 faintly visible ; accordingly a spherical mass of crystals surrounding a pearl has a dark 

 central space. 



In a vertical section of the sponge stained in borax-carmine the spheroidal 



