3 5 H THE SPONGES 



anchor the sponge in the mud. For a varying distance below the body, the tuft is 

 invested by a parasitic zoophyte. A transverse section of the cup shows a cavity, 

 in the centre of which is a spike which is the upper end of the glass-rope projecting 

 into the interior. From the central spike septa radiate; these are convex along their 

 upper margins, and attached at their ends to the imperforate bands on the opercu- 

 lum. The walls contain the much-folded layer of flagellated chambers. 



The spicules of the tuft are pointed at the upper end, and terminate below in 

 minute four-pronged anchors. Many of them are marked with a spiral ridge, mi- 

 nutely serrated on the upper edge, and thereby offering resistance to the uprooting of 

 the tuft from the mud. The length of specimens varies from twenty to thirty inches. 



The Japanese species' is obtained from off Tokyo, from a depth of three hundred 

 and forty-five fathoms, and is fished for with long lines, weighted and provided 

 with hooks, which are dragged along the bottom. Eighteen species have been 

 obtained from the Atlantic, Pacific, and Southern Oceans, from depths ranging 

 from a few hundred up to two thousand five hundred and fifty fathoms. The 

 allied Semperella, shown in the right-hand illustration of the colored plate, occurs 

 in one hundred fathoms off the Philippines. It forms a subcylindrical stock, about 

 twelve inches in length and two inches thick, terminating in a dense tuft about 

 three inches long. The lace-like skin covers a complicated labyrinth of tubes. 

 Another Philippine form {Polylophus} , represented in the lower right-hand corner 

 of the same plate, has small thick-walled hemispherical cups, with tufts of spicules 

 growing from conical projections on the walls, and passing down to form root tufts. 

 This sponge is remarkable for producing buds, which become detached and develop 

 into complete sponges. In the middle of the lower part of the plate is shown a 

 species of another genus, known as Periphragella from Japan, which forms a 

 curved funnel, on the outer wall of which is a network of tubes which have 

 branched off from the main body. In Farrea, seen in the lower left-hand corner 

 of the plate, the body is formed of forking branched glassy tubes, the walls of 

 which consist of spicules whose rays have fused into a rigid framework. Sdero- 

 thamnus, from three hundred and sixty fathoms off Timor, is a remarkable 

 Dictyonine sponge, which forms a bush two or three feet in height, with the 

 branches marked with a spiral band. 



Another beautiful type is Carpenter's glass-sponge (Pkeronema), shown in the 

 illustration on p. 3505, which consists of a thick-walled cup, narrowed at the orifice, 

 and giving origin below to a thick root tuft of spicules; the first specimens were 

 dredged from a depth of five hundred and thirty fathoms off the Faroe islands. 



Glass-sponges, with one or two exceptions, have been obtained in deep water, 

 from ninety to two thousand nine hundred fathoms. Previous to the deep-sea 

 dredging expeditions, specimens had been found in only a few localities, and the 

 procuring of them had been due more or less to accident. Thus the Japanese fisher- 

 men, while in quest of deep-sea fish, brought up glass-ropes, which became 

 marketable commodities. Similarly, the Malays found it would pay to explore for 

 submarine treasure, and constructed their bamboo dredge. 



Fossil Hexactinellida are found abundantly in the Chalk. The Ventriculites, 

 found in Chalk flints, are the skeletons or casts of glass-sponges. 



