280 Destructive Nature of the Boring Sponge. [ May, 
rows for the accommodation of this toiler of the sea. It is well 
known that this species and its allies are found filling systems of 
canals in the shells of many species of mollusks, both dead and 
alive, as well as in fragments of limestone, but it is probably rare 
to find it in such a vigorous condition of development as in the 
submerged cargo of marble referred to above. Mr. H. J. Carter 
believes that occasionally some of the parasitic species do not 
bore their habitation but develop freely in the same manner as 
ordinary non-parasitic forms. Bowerbank in his “ Monograph of 
the British Spongidæ,” mentions an affiliated species which is 
parasitic on a sea-weed, boring or dissolving away the soft parts and 
allowing the harder fibrous structures to remain as a means of 
support. 
It may be well to bear in mind that eesi sponges, notwith- 
standing the fact that they excavate their own habitations, are not 
parasites in the sense in which nematoid and cestoid worms are 
parasitic, as Haeckel, with his usual sagacity, points out in his 
Monograph of the Calcareous Sponges. : 
Dr. O. Schmidt observes (Brehm’s Thierleben), that, “ A large 
portion of the coasts of the Mediterranean and Adriatic seas is 
composed of calcareous material which, from its tendency to 
become eroded, has a broken, jagged aspect, giving it a peculiar 
and often attractive appearance. Of such broken Dalmatian 
coast one can certainly measure off some thousands of miles of 
strand, and where it does not descend too abruptly, large and 
small stones and fragments of rocks cover the ground. One can 
scarcely pick up one of these billions of stones without finding it 
more or less perforated with holes and eroded by Cliona, often to 
such a degree that the spongy remains of the apparently solid 
stone may be crushed in the hand.” The same writer farther 
observes : “ This brings us finally to the question, by what means 
does this sponge eat its way into the rock? One would first 
think of the siliceous needles as the cause, but we soon see that 
we must abandon the notion that this is the boring apparatus, 
since it must be borne in mind that such apparatus must be 
operated. Even though the protoplasm executes delicate fluc- 
tuating movements, so that in C/iona (Vioa), as in many other 
sponges, the needles are drawn into bundles, rows or series in 
particular directions, in any case, the force so exerted would 
not be sufficient to scrape or erode the lime rock with their 
