52 LABORATORY DIRECTIONS IN 



demonstrates that it is a protozoon. Living specimens of other protozoa 

 may be stained with acetic methyl green, if desired, to show the existence 

 of but one cell in each. 



16. If cells are attached to one another, all are alike. Examine 

 stained preparations of Epistylis and Carchesium. 



2. Phylum PORIFERA (Lat. porus = pore + ferre = to bear). 



Characteristics. 



2a. Aquatic, mostly marine. Spongilla is a fresh- water form. 



26. Usually radially symmetrical. Examine Grantia or other 

 sponge. How many planes can be passed through the longitudinal axis, 

 each dividing the body into two parts that are mirrored images of each 

 other? 



2c. Multicellular. Examine a cross-section of Grantia. Note that 

 many cells are present. 



2d. Diploblastic. Note also in the cross-section of the body that 

 there are two layers of cells, with a gelatinous substance between. 



2e. Numerous pores. Examine the surface of a dried specimen of 

 Grantia with a dissecting microscope. Also the inner surface of a 

 specimen split open (keep in alcohol or water). 



2/. Skeleton composed of spicules or spongin. For spicules examine 

 the surface of Grantia, the skeleton of Euplectella, and a slide bearing 

 isolated spicules of Grantia. For spongin, tear off a minute portion of a 

 bath sponge, place between two slides, and examine with a compound 

 microscope. 



3. Phylum CCELENTERATA (Gr. koilos = hollow + enteron = 

 intestine) . 



Characteristics. 



3a. Aquatic, mostly marine. Hydra, and at least one of the colonial 

 hydroids, are fresh- water forms. 



36. Diploblastic. Examine a cross-section of Hydra. Note the two 

 layers of cells. 



3c. Radially symmetrical. How many planes can be passed through 

 the longitudinal axis of Hydra, each dividing the body into halves approxi- 

 mately mirrored images of one another? How many such planes through 

 the jelly-fish Gonionemus? Through a hydranth of Obelia? The sea- 

 anemone Metridium? The coral Fungia? 



3d. Single gastro vascular cavity. Note the hollow interior of Hydra 

 as shown in cross-sections. Observe also the coenosarc of Obelia. 



3e. Nematocysts. Examine these in preparations of Hydra and 

 hydranths of Obelia. In the tentacles of Gonionemus. If living ma- 

 terial is available, examine nematocysts of Hydra that have been 

 discharged. 



