358 A MONOGRAPH OF THE 



Bailee, during his deep sea dredging at Shetland, in 1858. 

 It encrusts a portion of the valve of a Pecten, covering a 

 space about half an inch in length and the eighth of an 

 inch in breadth, and it does not exceed half a line in thick- 

 ness. The ovaries are numerous and closely packed toge- 

 ther, and are distinctly visible with the unassisted eye, 

 looking like very minute yellow cocoons of some terres- 

 trial insects, and were nearly thirty in number, on an area 

 equal to about a quarter of an inch. The whole sponge is 

 remarkably curious, forming a structural link between two 

 hitherto distinct tribes of Sponges ; that is, the genus 

 Spongia, with its solid cylindrical keratose fibre, and the 

 Halichondraceous tribe of sponges, with their purely reti- 

 culo-spiculous skeletons. 



The fibrous portion of the skeleton is very peculiar in 

 its character. It is smooth and cylindrical, having an axial 

 line of, generally speaking, single spicula, uniting at their 

 points, running throughout its whole length ; but when of 

 more than ordinary diameter, there are frequently other 

 spicula at intervals, imbedded in the fibre parallel to the 

 axial series. Throughout the whole length of the fibres at 

 short intervals, there are similar spicula to the axial ones, 

 imbedded at right angles to their axis, and projecting from 

 the surface for half or more than half of their length. 

 Some of these projecting spicula originate small lateral 

 branches of the keratose skeleton, but by far the greater 

 portion of them are the connecting points of the keratose 

 fibres, and the reticulated portion of the skeleton, the 

 former being thus completely imbedded amidst the latter. 



The ovaries are attached by the sides to one or more 

 branches of the fibrous skeleton, and they are also intimately 

 connected with the reticulated skeleton by the uniting of 

 the spicula of the latter with those of the surface of the 

 ovary. The wall of the ovary is very thin, and appears to 

 consist of a single membrane, profusely furnished with 

 spicula which cross each other in every direction, and occa- 

 sionally appear to assume a somewhat fasciculated arrange- 

 ment. They are not uniform in shape, some being regu- 

 larly oval, while others are more or less ovoid. I could not 



