REPORT ON THE HEXACTINELLIDA. 133 



siliceous matter or a drop of fat. On the outside of the sponge, in fine tangential 

 sections, the small dermal pores could be detected in the quadrate meshes of the dermal 

 skeleton. 



This genus contains only a single species. 



Polylophus philippinensis, (Gray) (PL LIII. figs. 1, 2 ; PI. LIV.). 



Some very young spherical or egg-shaped specimens of Polylophus [Rossella, Gray) 

 philqypinensis, Gray, were procured, along \vith Lanugmella pupa, 0. Schmidt, near Little 

 Ki Island (Station 192) from a depth of 129 fathoms. But besides these, numerous 

 adult forms of the same species were collected near the Philippine Island, Zebu (Station 

 209, lat. 10° 14' N., long. 12,3° 54' E.), from a depth of 95 fathoms and a blue mud 

 bottom. Some of these specimens were as large as a man's fist. They agree exactly 

 with the careful description and figure given by Carter^ and by Marshall. All the 

 specimens exhibited a short, thick-walled, cup-form, with a wide round upper opening to 

 the simple sack-like gastral cavity. Into the latter the efferent canals open with more or 

 less wide round apertures, while the outer surface, covered with a fine lattice network, 

 is elevated into numerous mammilla-like papillae. From the summit of each of these 

 radially disposed papiUse, which are especially thick and long on the lower surface of the 

 body, a thin bundle or tuft of long hair-like siliceous spicules projects. On the upper 

 and lateral surfaces these tufts of needles stand out radially, stifi" and straight ; on the 

 median and basal papillae, however, the siliceous hairs are much longer, and are apposed 

 to one another to form a long, broad, loose root-tuft, by which the sponge is anchored in 

 the mud (PI. LIV. fig. 1). Very frequently, on the larger specimens, some or most of 

 the papillary elevations are thickened terminally in a club-shaped fashion, and more or 

 less markedly constricted at the base, so as to form pear-shaped appendages represented 

 by a whole series of stages varpng greatly in size and difierentiation. Each protuberance 

 begins as a small conical, subsequently pear-shaped, structure 2 to 3 mm. in length, and 

 attains the size of a hazel nut. Fully developed forms exhibit lateral radial papillae, 

 and a basal radial tuft, while at the upper pole a circular aperture communicates with 

 the central cavity. The whole form of a young Pohjlophus is thus assumed, and it 

 remains connected to the mother organism merely by a few spicules. These give way of 

 themselves, and a small form is set free which imdeniably resembles the mother sponge 

 in all essential points (PI. LIV. fig. l). It is noteworthy that almost all the larger 

 specimens exhibit that tendency to form buds which has been repeatedly noted by 

 earlier observers. Between the papillae the external skin-covering appears to be as 

 smooth as the concave interior surface of the gastral cavity. On the simple, somewhat 

 sharp-edged oscular margin, there is no trace of a cufl'-like marginal fringe of spicules. 



• Ann. and Mag. Nat. Hist, ser. 4, vol. xv., pi. x. fig. 1. 



