22 DR. J. S. BOWERBANK ON HYALONEMA HIRABILE. [Jan. 10, 



of preservation is in the collection of the Bristol Museum. Numerous 

 other specimens are now known, of which the spiral clbacal cohimn 

 alone has been preserved by the Japanese fishermen who took them ; 

 and of such specimens 1 have had nineteen in my possession. Of 

 these, five had none of the coriaceous dermis around the spiral column. 

 Three specimens from the collection of my friend Capt. Charles 

 Tyler had portions of the basal mass of sponge closely adhering to 

 the proximal end of the column, and one of these three has every 

 appearance of having been accidentally withdrawn from the original 

 basal mass of sjionge some time previously to its being taken by the 

 Japanese, as there is, about f of an inch above the proximal end of 

 the spiral column, a small bulbous mass of the sponge remaining, 

 nearly an inch in length (PI. IV. fig. \). This small mass has se- 

 creted a new thin brown dermal membrane, which is continued 

 upward for about an inch, closely surrounding the spiral column. 

 It then throws out ten or tv/elve of the mammiform oscular bodies 

 in the course of about another inch of its progress upwards, the 

 remainder of the spiral axis being in a denuded state. The mem- 

 brane surrounding the bulbous mass of sponge and that closely 

 embracing the spiral column above it are continuous and identical in 

 structure, thus affording unmistakeable evidence of their forming 

 parts of one and the same animal. The specimen represented in 

 PI. IV. fig. 2 has the spiral column enveloped by the corium from 

 its junction with the distal end of the basal sponge for about 2 inches 

 upward, but it does not enter its substance. The dermal membrane 

 of the sponge is entirely wanting. 



Two of the nineteen specimens had their distal terminations en- 

 tirely covered by the coriaceous dermis of the column ; and several 

 of them had the thinning off of the proximal extremity of the dermis 

 of the column at the point of its junction with the thin dermal mem- 

 brane of the distal end of the basal mass of the sponge ; so that 

 between the whole of the specimens there is no part of the entire 

 sponge which is not duly represented. 



The basal mass of the sponge in the British Museum collection is 

 of a compressed massive form ; it is 54 inches in height, .S| inches 

 in width, and nearly 1 1 inch in thickness ; the total height, inclu- 

 ding the cloacal cohunn, is 20 inches. The base of the spiral axis 

 of the cloacal appendage is at or near the base of the sponge ; and it 

 passes thence in a vertical direction through its substance, emerging 

 at its distal extremity. The surface of the spongeous mass has every 

 appearance of having been smooth and even. 



The great cloacal organ and its oscula are exceedingly interesting 

 in their structure. While the spiral axis of the cloaca is surrounded 

 by the basal spongeous mass, it has no dermal investment of any 

 kind ; but as soon as it emerges from its distal extremity the thin 

 dermal membrane of the sponge is continued over the surface of the 

 column, and gradually thickens in its course upward, unlil it assumes 

 the form of a .stout coriaceous investment, and it then becomes com- 

 posed of two distinct layers, the outer one being thickly studded 

 with grains of sand and other extraneous substances, which do not 



