336 THE AMERICAN MONTHLY [Dec 



tlian mere theoretical knowledge gained from twenty 

 pages of a museum catalogue. 



The first named in the list is Leucosolenia atolonifer, 

 and a more useful sponge can scarcely be found for our 

 first study, because of its extreme simplicity of form and 

 structure. We are fortunate in having so simple a sponge 

 so close at home. It consists of a colony of three or four 

 very thin walled tubes springing vertically from a slender 

 rootlike bar of sponge tissue running horizontally along 

 the surface of the weed to which the colony is attached by 

 down-growing processes. Each tube reaches a height of 

 about 1| incUes, having a thickness of J-inch, At the 

 very top of the tube is the osculum for the outgoing stream 

 of water. A thin section across one of the tubes shows an 

 extremely thin wall pierced by pores which communicate 

 directly by means of narrow canals, with the central cav- 

 ity which alone is lined by collared cells. The existence 

 of the simplest possible canal-system and the absence of 

 flagellate chambers render this sponge especially accept- 

 able to a novice in spongology. There is little to learn 

 about it, but this little must be learned before any real 

 progress can be made with the anatomy of the more com- 

 plicated forms. The sponge, unfortunately, is not of com- 

 mon occurrence, only one specimen, creamy white in color, 

 being captured during the visit ; and that one was found 

 attached to a piece of seaweed floating in with the in- 

 coming tide. 



Closely allied, in relationship, to L. stolonifer, but dif- 

 fering entirely from it in appearance, is L. stipitata, found 

 in considerable numbers attached to the under surface of 

 loose stones. Its somewhat oval body is fixed to the stone 

 by a short slender stem — body and stem together meas- 

 uring somewhat less tiian |-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 



