Mr. A. Hancock on the Excavating Sponges. 235 



and aiTangement_, and with the same kind of spicula_, always 

 occupy similar burrows. 



7. That the oscula or papillae always correspond in size, 

 number, and position to the external orifices in the surface of 

 the shell or stone enclosing the sponge. 



8. That Cliona has been traced through every stage of growth, 

 from the microscopic gcmmule adding branch after branch and 

 lobe after lobe, to the fully developed sponge, excavating step 

 by step its complicated abode in sound transparent shell *. 



Cliona undoubtedly works out the cavities it inhabits, whether 

 mechanically or otherwise. Whatever the process may be, the 

 difficulty in believing that a sponge, even if deprived of all 

 mechanical agency, can burrow into hard substances is much 

 lessened since I first wrote on the subject. It has recently been 

 ascertained that some of the Polyzoa bury themselves in hard 

 calcareous bodies, as does also Lagotia vii-idisy a minute and 

 feeble animalculef ; and it is now well known that certain uni- 

 cellular Fungi live immersed in the shells of mollusks and in 

 other hard calcareous bodies J. And, surely, since such is the 

 case, since plants, without motion or any mechanical aid, work 

 out for themselves crypts and channels in hard shell, there can 

 be no difficulty in the way of believing in. the possibility of a 

 sponge forming its habitation within substances of the same 

 nature. And it is interesting to observe how similar the ramifi- 

 cations of these Fungi are to those of Cliona, the resemblance 

 being so close in many instances as to lead to the idea that they 

 might prove to be microscopic sponges, had we not the high 

 authority of Kolliker for believing in their fungoid nature. 



Before concluding these few remarks, a word or two may be 

 said on a certain relation that appears to exist between Cliona 

 and the Foraminifera. All the excavating Sponges display a 

 lobed structure, some of them to a very remarkable degree. The 

 lobes are usually angulated, sometimes more or less rounded, and 

 are always connected together by exceedingly short constricted 

 stems into branches which, dividing dichotomously, anastomose, 

 the division and anastomosis usually going on to such an extent 

 that the sponge ultimately becomes a congeries of small lobes. 

 Now the sarcode of the Foraminifera is generally composed of a 

 scries of similar lobes, which are united in like manner by short 

 constricted stems, or ^'stolons," as they are called, only differ- 



♦ Ann. & Mag. Nat. Hist. ser. 2. vol. iii. p. 327, ph H. fig. 4. 



t Described by Strethill Wrijrht, M.D., in Edinburgh New Philosophical 

 Journal, new series, vol. vii. p. 276. 



X " On the frequent occurrence of Vegetable Parasites in the hard 

 structures of Animals," bv Prof. Kolliker, Ann. & Mag. Nat. Hist. ser. 3. 

 ▼ol.iv. p.SOO, Oct. 1859." 



