1900] MICROSCOPICAL JOURNAL 33'? 



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

 or pseudo-pores, and on the top ridge a single osculum 

 usuallj' occurs. The arrangement of the spicules which 

 form the skeleton can be easily seen if the sponge is ren- 

 dered transparent and mounted for microscopical exam- 

 ination. 



A few examples of L. pulcherrima 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. Tlie sponges 

 then take up a vertical position which allows them to be 

 readily seen and removed. 



Leaving the Homocoela group we take for our next con- 

 sideration Sycon raphanus which furnishes a higher type 

 of canal-system than the examples we have already stud- 

 ied. The body of this sponge, pine-apple in shape, is perch- 

 ed on a short stalk which anchors it to the stone upon 

 which it grows. In height it is usually less that ^-inch, 

 and it occurs singly or in colonies Csee Fig. A), each col- 

 ony furnishing individuals in all stages of growth. Grrow- 

 ing very close to the surface of the stone it is usually al- 

 most covered up with sand. This can be got rid of by re- 

 moving the sponges to a small bottle of sea water or 

 methylated spirit and gently shaking the same ; succes- 

 sive 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 appear- 

 ance to the fact that the ends of the flagellate chambers 

 which are developed as outgrowths from the central cav- 

 ity, project freely to the exterior and are protected exter- 

 nally 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. stolouifer), 



