REPORT ON THE HEXACTINELLIDA. 235 



extremity, from which project numerous fascicles of siliceous threads. The sponge body 

 is of a light brown hue, and rigid to the feel. Its surface exhibits an intricate interlace- 

 ment of the sponge tissue, which appears mainly composed of stellate, siliceous spicules 

 of various sizes. The coarser spicules of the surface have five rays. Four of these 

 together are irregularly cruciform, while the fifth projects in a direction opposite to all the 

 others. They appear to be so arranged that the crucial rays interlace with those of the 

 contiguous spicules forming a lattice-work on the surface of the sponge, while the odd ray 

 opposed to the others penetrates the interior of the sponge. The finer tissue, seen 

 through the intervals of the latticed arrangement on the surface of the sponge, appears to 

 I)e made up in the same manner of finer stellate spicules. Some of the longest stellate 

 spicules of the surface have a spread of half an inch. 



" The fascicles of siliceous threads projecting from the body of the sponge are upwards 

 of twenty in number, and over 2 inches in length. They resemble in appearance tufts 

 of blonde human hair. The individual threads are nearly like those proceeding from the 

 lower end of Euplectella. Where thickest, they are less than the ^^^ of an inch in 

 diameter, and become attenuated towards the extremities. At first, as they proceed from 

 the body of the sponge, they are smooth and then finely tuberculate. The tubercles 

 are gradually replaced by minute recurved hooks, which become better developed 

 approaching the free end of the threads, which finally terminate in a pair of longer 

 opposed hooks, reminding one of the arms of an anchor. The objects of the tufts of 

 threads, with their lateral booklets and terminal anchors, would appear to be to maintain 

 or moor the sponge in position in its ocean home." 



Without knowing of these publications by Leidy, Wyville Thomson had in 1869 

 given a detailed and thorough account of a sponge designated Holtenia carpenteri, 

 several specimens of which he had collected to the north-west of Scotland, from a 

 depth of 530 fathoms in the course of his deep sea investigations in the " Lightning." 

 The form of these specimens, which were about as large as one's fist, was " globular, 

 elliptical or subcylindrical." A spacious and tolerably smooth central cavity, half the 

 diameter of the sponge, diminishes superiorly to a round space of perfectl}'' uniform 

 breadth, while from the closed under side a tuft of numerous individual clusters of 

 tolerably long, bow-shaped siliceous spicules doubtless rooted in the sand, runs out 

 in a radial direction. On the lateral wall, and most abundantly near the upper surface, 

 long radially directed spicules project freely, while the boundary of the wide superior 

 osculum is formed by a compact wreath of vertical spicules measuring about 1 cm. or 

 more in length. Both on the outer and inner surfaces of the tolerably firm cup-shaped 

 sponge body, a firm rind is formed of strong compact siliceous spicules which lie in 

 the skin, and are grouped together in stellate fashion, while the parenchymal mass itself 

 is penetrated by a system of numerous cavities and canals. The siliceous spicules which 

 penetrate and cover the entire organism resemble generally those of Hyalonema. The 



