230 A MONOGRAPH OF THE 



Locality. — All parts of the Coasts of Great Britain. 

 Examined. — Alive. 



The shape of this sponge varies exceedingly. In its 

 young condition it forms a thin smooth coating, on stones 

 or fuci, frequently not exceeding three or four lines in 

 thickness, or it envelops the stems of small Fuci or Zoophytes, 

 and ultimately becomes free rolling masses of every variety 

 of shape ; or if it remains adherent to its original attach- 

 ment, it becomes thick and massive, or it is projected in 

 the form of one or more thick, elevated ridges, and it is then 

 the cock's comb sponge of Ellis. In its greatest degree of 

 development it frequently assumes a fistulous form. In the 

 living state the surface is smooth and even, but in the dried 

 condition it presents a structural character by which, when 

 once familiar to the eye, the species may be almost always 

 easily detected ; and that is a beautifully reticulated appear- 

 ance of the surface when viewed by an inch lens. This 

 character is not inherent in the dermal membrane, but is 

 simply an impress of the reticulated skeleton of the sponge 

 immediately beneath its surface, and is therefore a constant 

 character, and one the like of which I do not remember to 

 have seen in any other British species of sponge. 



The oscula when on the surface are large, irregularly dis- 

 persed, sometimes perfectly simple orifices, at others thinly 

 margined or slightly elevated, and mammseform ; but when 

 collected in fistulse, they are always simple. The fistula? 

 vary much in size and form. In one little specimen col- 

 lected in the Menai Straits near Bangor, the whole sponge 

 had assumed the form of five or six fistulse, each about 

 three lines in diameter, and about a quarter of an inch in 

 height, thus very closely simulating a small specimen of 

 Polymastia mammillaris. In specimens from Tenby the 

 fistulse are projected about an inch and half in height, and 

 exceed half an inch in diameter ; from Fowey in Cornwall 

 I have them from my indefatigable friend Mr. Peach, 

 exceeding six inches in length and three quarters of an inch 

 in diameter ; and in a very fine specimen from Belfast 

 Lough, sent to me by my late friend Mr. Wm. Thompson. 



