APPENDIX 



563 



On rocky parts of the coast Obelia and other hydroids may be 

 found at low tide. They will travel alive in a vessel of 

 Obelia. sea water. 



1. Note retraction of polyp heads when touched or 

 shaken. 

 2. Kill a twig by dropping osmic acid suddenly on to it when it is 

 in a small quantity of water, with tentacles expanded. Stain 

 and mount. Note : hydranths, with tentacles and mouth, 

 ccenosarc, gonangia, peritheca, hydrothecae (Figs. 108, 109). 



10. Examine a vertical section of a hydranth (Fig. no). 



11. Examine a medusa, stained and mounted (Fig 113), 



.-ervd- 



FlG. 403. — Portions of tentacles of Hydra magnified. 



A, Moderately contracted ; B, moderately extended. 

 bat.. Batteries; cnc, cnidocil; ect., ectoderm; end., endoderm ; ntc, nemato- 



cysts. 

 Some of the batteries, and parts of others, are seen through the thickness of the 



tentacle. 



Fresh specimens of the Liver Fluke can only be obtained when a 

 sheep infected with them is killed. Laboratory specimens 

 The Liver Fluke.are usually preserved in formalin. 



2. Note : mouth, ventral sucker, genital pore 

 (Fig. 121). 



3. Dry the surface of the body and under a lens note spicules. 



4. In a specimen which has been fixed while it was flattened 



under pressure and mounted in balsam, note : pharynx, 



intestinal casca ; testes, cirrus sac ; ovary, yolk glands, 



uterus, shell gland (Figs. 122, 124). 

 In an injected specimen, observe excretory system (Fig. 122). 

 Examine a transverse section through the region of the ovary 



(Fig. 404). 

 Stages of the life-history should be examined if available 



(Fig. 125). 



5- 

 10. 



