of Foreign Bodies hij Sponges. 309 



fibre. It can liardly be supj)osed that they fall on to the 

 fibre-tip and adhere in this position. 



In a sponge which I have described elsewhere as Enspongia 

 officinaHs, ? var. rotunda, the following points are to be noted : — 

 Tiie cortex is closely like that of Migas porphyrion, but deeper, 

 and, being free from loose sand-grains, is easy to cut. The 

 whole appearance suggests a tissue of wliicli the cells are in 

 active motion. There is an abundance of amoeboid granular 

 cells (like the smaller granular cells of Migas parphyrion) ; 

 in places these form, as it were, streams of fusiform cells, but 

 in other places the cell-bodies are more massive and crowded 

 together. Often when the aggregation occurs at the surface 

 the latter has minute irregularities, suggesting pseudopodia. 

 Where foreign spicules are to be found just beginning to 

 pass into the sponge there are clustered lobose granular 

 cells (tig. 4). An argument which seems to me to be worth 



Fig. 4. 



Frotn the surface of Euspongia officinnlis, ? var. rotunda, 

 s, foreign spicule t'ragnuent. 



considering is this : within the cortex are scattered spicular 

 fragments lying" more or less parallel to the surface and 

 obviously occupying the position which they had in the 

 living sponge (Hg. 5). Now the main fibres alone contain 

 foreign bodies, and there are no free spicule fragments in the 

 deeper parts of the sponge. What, then, is the meaning of 

 this temporary position of the spicule fragments if it is not 

 that they are on their way to the main tibres to which they 

 are being carried by the granular cells? It is ditticult to 

 understand the concerted action of amccbocytes, but it is not 

 more diflicult in this case than in that of the wonderful 

 migrations of cells carrying spicules with them which Evans 

 has shown to occur during the formation of the gemnuile- 

 coat of iSjjoiigiild. Cotte attributes the, excavating power of 



