70 THE VICTORIAN NATURALIST. 



numbers attached to the under surface of loose stones. Its some- 

 what oval body is fixed to the stone by a short slender stem — body 

 and stem together measuring somewhat less than %-inch. The 

 sponge is built up of a complicated system of branching and 

 anastomosing tubes, each of which is of the same type of structure 

 as the simple tube of L. stolonifer. When viewed, under the 

 lens, the wall is seen to be pierced with fairly large holes or pseudo- 

 pores, and on the top ridge a single osculum usually occurs. The 

 arrangement of the spicules which form the skeleton can be 

 easily seen if the sponge is rendered transparent and mounted for 

 microscopical examination. 



A few examples of L. pidcherrima are also to be found living 

 side by side with L. stipitata to which they are very similar in 

 size and appearance. 



In order to collect specimens of these small sponges the stone 

 to which they are attached should be placed in water just deep 

 enough to cover the surface of it. The sponges then take up a 

 vertical position which allows them to be readily seen and 

 removed. 



Leaving the Homoccela group we take for our next consideration 

 Syconraphanus which furnishes a higher type of canal-system 

 than the examples we have already studied. The body of this 

 sponge, pine-apple in shape, is perched on a short stalk which 

 anchors it to the stone upon which it grows. In height it is usually 

 less than ^-inch, and it occurs singly or in colonies (see 

 Fig. A), each colony furnishing individuals in all stages of 

 growth. Growing very close to the surface of the stone 

 it is usually almost covered up with sand. This can be got rid of 

 by removing the sponges to a small bottle of sea water or methy- 

 lated spirit and gently shaking the same ; successive changes to a 

 fresh supply of water or spirit soon render the sponge fit for 

 examination. 



If a thin transverse section is examined it shows at once that 

 the sponge owes its characteristic pine-apple appearance to the 

 fact that the ends of the flagellate chambers which are developed 

 as outgrowths from the central cavity project freely to the exterior 

 and are protected externally by a special arrangement of one-rayed 

 spicules which stand out like stiff spines. Each chamber is built 

 upon the same plan as our simple type of sponge (L. stolonifer), 

 but in place of a simple tube with its one exhalent opening, there 

 are here hundreds of simple tubes, not leading an independent 

 existence but all connected with and opening into one central 

 cavity, which, in turn, opens to the exterior by one osculum. The 

 water enters directly into the flagellate chambers by means of 

 prosopyles which occur freely in the part of the wall exposed to 

 the sea ; then it flows through the chamber and so into the 

 common central cavity, finally passing out of the sponge by the 

 osculum at the top. 



