SPONGES 



The Sponge Skeleton. — Examine carefully a piece of 

 commercial sponge. Note the location of the smaller and 

 larger openings and their relation to one another. Make 

 out the general circulation of the water in the sponge and 

 make a diagramatic section of the sponge showing the 

 system of circulatory tubes. 



Tear off a piece of the sponge and mount it in water under 

 a cover glass. Are the fibers single threads or branched? 

 Describe briefly the structure and make a drawing showing 

 the points noted. 



The Simple Sponge (Grantia ciliata). — (i) Gen- 

 eral Method of Examination: — The entire specimen should 

 be examined with the unaided eye and then with pocket 

 lens. Keep it in fifty per cent, alcohol in watch crystal while 

 examination proceeds. For making sections after the gen- 

 eral work is completed a sponge should be run through the 

 alcohols and stained (see Appendix, III), then mounted in 

 paraffin and cut into thin sections with the microtome. These 

 sections may be mounted in balsam after dissolving out 

 the paraffin with turpentine. Another specimen should be 

 prepared by allowing it to stand twenty-four to thirty-six 

 hours in two per cent, solution of chromic acid. This dis- 



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