270 B. W. PRIEST FURTHER REMARKS ON THE 



Mr. Hillier has also sent me up a foreign shell, where the per- 

 forations and cavities, though small, are completely filled with the 

 Sponge, and says, in the letter accompanying it, '^ Can you doubt 

 that the burrows are made by the Sponge ?" 



Even Dr. Bowerbank himself tells us that very few oyster, or 

 other shells in which the perforations exist, are free from this 

 Sponge, and yet he is trying hard to prove that it is only as a 

 parasite that it exists in them. It seems strange to me that, if such 

 is the case, the same species or class of Sponge should almost always 

 be found to occupy those cavities. 



That Carter, Hancock, and other naturalists should have made 

 a separate family of these Sponges under the name of Ecccelonida 

 — from the Greek, to hollow — is, I think, sufficient proof of their 

 belief in their excavating powers. The family is divided into three 

 genera — Cliona of Grant, Thoosa of Hancock, and Alectona of 

 Carter. 



Speaking of the last, which comprises the Alectona MiUarij which 

 excavates Corals in a most devastating way. Carter says that, like 

 Cliona celata, it leaves its burrows and grows up externally into a 

 massive form. 



Now the process by which this burrowing, boring, or excavating 

 is produced is another question. I think that I have said enough 

 to prove that the Sponge is capable of doing it. Certainly the nearest 

 approach of analogy is in what Mr. Stewart said at the last short 

 discussion on the subject, when he brought forward the markings 

 which appear in bones, where necrosis has, or is, taking place ; and 

 also similar markings which may be seen in the process of the for- 

 mation of bone in the femur of a fcetus, where, as the develojDment 

 of the bone proceeds, the calcified cartilage is absorbed, and larger 

 cancelli and canals formed. I have had the opportunity of examin- 

 ing very carefully sections with the process going on, and 1 have 

 there actually seen the protoplasm acting on the surrounding parts, 

 and to all appearances eating its way into them. 



One can hardly call that a mechanical process, but I feel certain 

 in my own mind that it is a similar sort of thing that takes place 

 with the burrowing Sponges. 



I hold with my friend Mr. Hillier that there are processes beyond 

 the mechanical, or even the chemical processes of the laboratory, 

 which we do not as yet thoroughly understand, but which may be 

 called vital for want i:>f a better term. Because we do not know how 



