LESSONS m ZOOLOGY. 



THE SPONGE. 



Lessox I. 



For the teaoher, » bath sponge with one or two large openings 

 on the top; for each child, a straight wire hairpin and a slate 

 sponge, are the things needfal for this lesson. Each sponge may 

 be oat vertically, almost to the base, throngh one of the large 

 tnbes, or vertical sections may be used with the whole sponges. 

 The day before the lesson, each child shonld wash ont his sponge 

 and notice bow it is changed by the water. Sponges shonld always 

 be moist when studied. The hairpins are straightened ont for nse 

 as probes. 



The children have already learned the following things : 



The hard, dry sponges took in water through all the 

 little holes, and became soft and elastic. They are made 

 of threads called fibres, whose ends project in little brush- 

 like bundles on every side but one, and this side is darker 

 and smoother than the others. There are many small 

 holes in the sponge, and only a few large ones, or some- 

 times only one. One or two bright pupils notice that 

 there are holes all through the sponge, and a large tube 

 running straight down from the large opening. 



Children will give some of these points spontaneonsly ; others 

 most be bronght ont by skillful questioning. 



Now, being careful not to tear the fibres, we put the 

 probes into the large openings, and trace the tubes (Fig. 

 1, a) into which they lead, almost to the base of the 



