202 A MONOGRAPH OF THE 



there is an extremely thin layer of the sponge looking like 

 dust within the mouth of the shell, and the angle within 

 the shell at the junction of the outer with the inner whorl, 

 is filled up to the breadth of about a line, and the depth of 

 half a line. From this it would appear that every minute 

 fragment of the sarcode of the sponge, although separated 

 from the parent mass, is capable of sustaining the life it 

 carries with it, and of multiplying the species by even this 

 minute mode of division. 



This mode of developing itself from a univalve shell is 

 also the habit of H. Jieus, which is by no means uncommon, 

 from the north-eastern coasts of England. There is one of 

 this description, based on the shell of a Pucus, that is in the 

 Museum at Newcastle-on-Tyne, which is projected in an 

 elongated flattened form to the length of seven and a half 

 inches, having several large lateral lobes, and not exceeding 

 an incb in thickness at any point, each lobe having one or more 

 oscula, the whole number of these organs being twelve or 

 thirteen, none of them exceeding the eighth of an inch in 

 diameter; but the difference between the two species is 

 readily determined by the presence in H. ficus of the 

 minute inflato-cylindrical, which abound on the inner 

 surface of its dermal membrane. 



In the neighbourhood of Tenby H. suberea is frequently 

 brought up by the oyster-dredgers, in masses as large as a 

 man's fist, without any appearance of shell, which has pro- 

 bably been entirely enclosed by the sponge ; in these speci- 

 mens two or three large oscula are usually found, and the 

 sponges are generally of a rich orange colour. I also found 

 a specimen as large as a hen's egg, attached by a broad 

 base to the side of St. Katherine's Rock, at Tenby, between 

 high and low water mark, showing that it is occasionally a 

 littoral as well as a deep-sea species ; but I have usually 

 found it on dredging in from 5 to 15 fathoms. 



