1875.] SPECIOSUM AND HYALONEMA MIRABILE, 609 
adds considerably to its strength ; and the membranes of the areas are 
abundantly supplied with the minute quadrihamate defensive spi- 
cula, which are all disposed on the membrane on their flat surfaces. 
In the structure of the upper portion of the dermal membrane the 
rete is open and diffuse, and the areas assume an irregular elongate 
form ; and the rete is composed only of large inflato-acerate spicula, 
without apparently any intermixture of the large rectangulate sex- 
radiate ones,which are of such common occurrence in the basal portion 
ofthe membrane. Another distinctive structural difference is, that the 
areas in the rete of the dermal membrane are furnished in a strikingly 
beautiful manner with the spinulate cruciform defensive spicula, 
which are abundantly disposed on all parts of the surface at nearly 
equal distances from each other in a manuer closely approaching 
regularity ; and nearly all of them are projected at right angles to the 
surface on which they are based. The minute quadrihamate spicula 
so abundant on the basal membrane are very rarely to be detected 
on the upper dermal one. 
These structural modifications of the dermal membrane indicate 
the difference in the respective offices of the two parts of the animal 
in a very striking manner ; but not to a greater extent than we may 
observe in many sessile British sponges under similar circumstances. 
A minute description of these characters of the respective parts of 
the dermis of the sponge are especially necessary, as much misappre- 
hension has existed in the minds of some naturalists as to the true 
position of Hyalonema in its natural locality, some having imagined 
that the pointed end was deeply plunged into the bottom of the sea, 
and that the sponge-mass was the distal termination of the animal.* 
In all sponges with which I am acquainted, the attachments are 
either adhesive, or clasping like the roots of Fuci, never penetrative 
like the roots of plants that derive nutriment from the soil, which 
sponges never do. The idea of the slender pointed distal termina- 
tion of Hyalonema being plunged into the sea-bottom, and thus 
supporting a heavy mass of sponge at its opposite end, is contrary to 
all we really know of the usual habits of these animals in their natural 
localities. In corroboration of this opinion, I may state that amongst 
the various specimens of this species of sponge which I possess, I 
have one thirteen inches in length, the distal extremity of which for 
six inches of its length is completely enveloped by the corium, which 
has the usua] mamilloid organs upon it up to the extreme apical 
termination. These organs, which have been supposed to be polyp- 
cells, would have been in a very strange position had they ever been 
immersed in the soft substance of the sea-bottom. In further elu- 
cidation of this subject, I may refer my readers to an article on 
Hyalonema in ‘ Land and Water,’ for February 13, 1871, p. 219, 
written, [ am informed, by a naval officer of the name of Templar. 
He writes :—“ For Dr. Bowerbank’s theory concerning Hyalonema, 
‘or the long glass-rope sponge,’ and his belief in the siliceous spicula 
growing upwards, the sponge adhering to a rock, I have great respect 
as well as belief. His friend, Mr. Henry Lee, wrote to me when in 
Japan to try and discover ‘if such was the ease ;’ and from what I 
39* 
