Chapter XIII : Objects of General Interest 91 



2. Place the animal in a little tepid water. Watch until it 

 is extended full length, then flood it quickly with hot corrosive 

 sublimate, or hot Gilson's fluid. The animal may be removed 

 after 10 or 15 minutes and washed thoroughly in 50 per cent, 

 alcohol to which a little tincture of iodine has been added. 



3. Stain for 24 hours in borax-carmine, or in Delafield's 

 hematoxylin diluted one-half with water. 



4. Wash in water followed by 35 and 50 per cent, alcohol 

 each 15 minutes. 



5. Decolorize in acid alcohol until the color ceases to come 

 away freely (10 to 30 minutes). 



6. Wash out the acid in 70 per cent, alcohol, using the alka- 

 line alcohol if hematoxylin was used in staining. 



7. Flatten the animal by compressing it between two slides 

 by means of a rubber band, and place it for 24 hours in 95 per 

 cent, alcohol. 



8. Transfer to absolute alcohol for 1 hour, and to xylol until 

 clear. 



9. Mount in balsam in a thin cell or without a cell at pleas- 

 ure. If on examination the separate organs of the animal are 

 not seen distinctly, the reason is probably that the object has not 

 been compressed sufficiently. This difficulty 'may also sometimes 

 be overcome in a measure by letting a cover-glass rest upon the 

 live Planarian to flatten it out slightly, and then running the fixing 

 fluid under the cover. Specimens which have been in the labo- 

 ratory for some weeks or months make better preparations than 

 those fresh from the stream. 



B. Mosquito, Gnat, or Aphid. 1. Kill a mosquito with cya- 

 nide or chloroform and place it in cedar oil or turpentine for an 

 hour. 



2. Remove, and place it on its back on filter paper. Care- 

 fully spread the legs of the insect, put a drop of thick balsam on 

 a slide, invert the slide, and bring the balsam in contact with the 

 thorax of the mosquito. Spread the wings and the legs of the 

 insect and gently press it down into the balsam. 



3. Add thinner balsam, see that the proboscis and antennae 



