IV PRACTICAL DIRECTIONS 317 



large eclodcnn cells. These extend longitudinally, and lie against the 

 outer surface of the supporting lamella. Sketch. 



Examine transverse sections through the body or tentacles, prepared 

 as directed on p. 136, after killing and fixing the^ specimens as 

 above. Work through 6— S again, noting the various cells and their 

 nuclei, &c. Observe especially — 



13. {a) The contractile processes of the ectoderm cells, which will be cut 

 across transversely, so as to appear as dots just outside the supporting 

 lamella ; (b) the aiiia-boid and vacuolated character of the cndodertii cells. 

 (Special methods of preparation are necessary in order t'j show the 

 flagella.) Sketch. 



Bougainvillea.^ 



If possible, examine first ali\e, and then kill and stain as directed in 

 the case of Hydra. Examine under the microscope and note : — 



(I. Colonial stage, i. The /z>'a'nr////w, attached to a common branching 

 stem : compare their structure with that of Hydra. 2. The medusa- 

 buds. 3. The cuticular exoskcleton supporting the colony. 



b. Medusa stage. I. The umbrella, leiitacks, velum, ma)iubrium, 

 mouth, radial a.nd circular canals, ocelli, m^d go/tads. 



'■ Specimens li\'ing or preserved, both of the colonial and medusa 

 stage of Bougainvillea or some allied form (e.g. Obelid), can be obtained 

 from any Marine Biological Laboratory ; or the fresh-water Cordylophora 

 will answer the purpose as far as the colony is concerned, Ijut it has no 

 medusa stage. 



