E. MAKSHALLI. — GEX. CHHRACTERS. 93 



of the lateral wall ceases to exist just around the bottom-plate, 

 so that the texture of the latter is entirely soft, being nearly 

 exactly like that of the parietal ledges. There can be no doubt 

 whatever that the round perforations of the plate are morpholo- 

 gically and functionally the same as the parietal oscula or the 

 sieve-plate meshes. In the main middle portion of the bottom- 

 plate, the oscula are irregularly scattered, while in the periphery 

 directly adjoining the last circular beam of the skeletal frame- 

 Avork, they are somewhat larger and more closely set, leaving 

 between them narrow beams by which the more central portion 

 of the plate is attached to tlie lateral wall. The plate therefore 

 most easily breaks oft' at these weak points iu the periphery. 

 The internal surface shows a number of small excurrent aper- 

 tures ; the external surface appears essentially the same as that 

 of the lateral wall. 



The bundles of basal anchoring spicules emerge from the 

 lateral wall in a circle near the juncture of the latter with the 

 bottom-plate, soon to form a soft and silky basal tuft iu the usual 

 manner. Since now, as already noticed, the lower end of the 

 sponge-body is compressed, the inverted hollow cone formed by 

 the basal spicules immediately after their emanation from the wall, 

 is likewise laterally flattened. More properly speaking, this primal 

 portion of the basal tuft is wedge-like in shape. It is perfectly 

 free of foreign objects interlocked among the fibers and I have no 

 doubt that this portion stands above and clear of the surface of 

 the substratum. Now, the compressed state of the tuft just before 

 it strikes root into the substratum, would give to the sponge a 

 greater freedom for swaying in one direction than iu any other. 

 I think it quite likely that this circumstance stands in a definite 



