THE EXCAVATING SPONGES. 345 



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

 cellular Fungi live immersed in the shells of mollusks and in 

 other hard calcareous bodies. f 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 na- 

 ture. And it is interesting to observe how similar the ramifica- 

 tions 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 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, or more or less rounded, and are 

 always connected together by exceedingly short constricted stems 

 into branches, which dividing dichotomously anastomose, the divi- 

 sion and anastomoses 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 series of 

 similar lobes, which are united in like manner by short con- 

 stricted stems, or "stolons," as they are called, only differing 

 from Cliona in the fact that they are usually arranged either 

 spirally or cyclically, and do not assume a regularly branched 

 character ; but nevertheless the arrangement of the lobes in the 

 two groups is occasionally very similar. 



If we remove the testaceous covering of any of the Rotalince 

 and suppose the sarcode unrolled, we shall see at once how much 

 the structure resembles a branch of Cliona corallinoides for in- 

 stance : both are composed of a series of nodules or lobes united 

 by very short constricted stems. The sarcode of JVbdosaria, 



* Described by Strethill Wright, M.D., in the Edinburgh New Philosophical Journal, new 

 Series, Vol. VII, p. 276. 



t •'On the frequent occurrence of vegetable parasites in the hard structures of animals." 

 Ann. and Mag. of Nat. His*., 3rd Scries. Vol. IV. p, 300, Oct., 1859. 



Z 



