Appendix D: Preparation of Microscopical Material 219 



sky blue through the addition of methylen blue solution made up 

 as follows: 



Methylen blue 1.0 gram 



Castile soap 0.5 gram 



Water 300.0 c.c. 



After two hours the hydra may be transferred to fresh water; the 

 nematocyst cells are stained a deep blue. (Method of Little, 

 Journal of Applied Microscopy, Vol. VI, p. 2116.) 



To Discharge Nematocysts drum on the cover-glass gently with 

 a pencil. By using a very small opening to the diaphragm they 

 are usually sufficiently distinct without staining. 



For Other Polypoid Forms, the methods given for hydra will 

 answer in most cases. 



For Collecting Free-Swimming Medusoid Forms full directions 

 will be found in Brook's Invertebrate Zoology. 



Compound Hydrozoa should be placed alive into the cells which 

 they are to occupy when mounted. One per cent, formic acid is 

 then added drop by drop to the sea-water. After the animals 

 have been killed, the fluid is replaced by glycerin-jelly and the 

 cover-glass is put in place. Another method is to kill the animals 

 slowly by adding a few crystals of chloral hydrate, from time to 

 time, to the small vessel of sea- water containing them. 



Small Jelly-Fish may be fixed and hardened in 1 per cent, 

 osmic acid and, stained or unstained, mounted in cells. 



PLAN ARIA 



Look for planarians on the under sides of stones in small 

 streams of running water. They are usually examined alive. To 

 see them thrust out the proboscis, keep them from food for a few 

 days and then feed them on dead flies. Planaria which have been 

 kept in the laboratory for months display the internal organs 

 much more clearly than freshly captured ones. 



If it is desired to study stained specimens, for preparation see 

 chap, xiii, iv, A. 



To Kill Planaria with Pharynx Protruded Cole (Journal of Ap- 

 plied Microscopy, Vol. VI, p. 2125) recommends covering 



