14 E. B. Williamson 



or bottles of specimens kept in the dark. After a few days the ak^ohol in 

 which they are preserved should l3e replaced with clean, full-strength 

 alcohol. 



THE PRESERVATION OE NYMPHS. 



Mr. R. J. Tillyard recommends the following formula for preserving 

 larvse where preservation of internal parts is desired. 



15 parts 98% alcohol. 

 6 parts JFormal. 

 2 parts glacial acetic acid. 



30 parts distilled water. 



Place larvse in this alive. As soon as possible make ventral incision 

 opposite mid-gut. After 24 hours preserve in 70% alcohol. 



Professor James G. Needham, in reply to my inquiry about any special 

 methods, wrote, "I simply use alcohol and, when particularly careful, change 

 it a time or two within a few days after putting specimens in and endeavor 

 to have it, when osmosis is complete, of a strength of 70-80%. Preserva- 

 tion of the nymphs is then entirely satisfactory. I have found formalin an 

 abomination, as it does not penetrate and does make brittle. The glycerine 

 mixtures make things greasy, so I have ended up by using the method that is 

 simplified." 



THE PRESERVATION OF NYMPHS AND IMAGOES EOR HISTOLOGICAL AND 

 CYTOLOGICAL STUDIES. 



The following notes on preservation of nymphs and imagoes for his- 

 tological and cytological work have been kindly furnished by Dr. Philip 

 P. Calvert of the University of Pennsylvania. 



Larvse and imagoes of Odonata may be fixed and preserved for study of 

 internal organs as follows. Plunge the living insect into hot water, hot 

 alcohol (30-50%) or hot Gilson's fixing mixture. The temperature should 

 'be 8o°-90°C. Gilson's mixture is composed of nitric acid (46° strength) 

 78 cc, glacial acetic acid 22 cc, corrosive sublimate 95 grams, 60% alcohol 

 500 cc, distilled water 4400 cc. When the entire larva or imago is to be 

 preserved for dissection, and not for histological or cytological work, hot 

 water or hot alcohol (as above) will suffice. The insect should be left in 

 them only until muscular movements cease, then withdrawn from the liquid, 

 one or more slits cut through the chitin (according to the size of the speci- 

 men) in places where internal organs will not be injured, always taking 

 care to cut no deeper than through the chitin and underlying hypodermis, 

 and immediately placed in alcohol of greater strength than that employed 

 for fixing. After one or more hours this alcohol should be replaced with 

 stronger and so on until a strength of 70 or 75% is reached. When Gilson's 

 •mixture is used, the specimen should be (after cutting the slits) washed in 

 water for an hour or more to remove the mercury salts. 



When internal organs are desired for histological or cytological work, 

 section-cutting, etc., the insect should be cut in pieces as it is allowed to 

 fall into the killing fluid. This is for the purpose of affording more rapid 



