ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1045 



(2) Preparing- Objects. 



Preparing Supra-oesophageal Ganglia of Orthoptera.* — Signer G. Cuc- 

 cato snips otf the head of the insect with a pair of scissors, and pins it on 

 cork. Thus fixed, the head is immersed in 0-75 per cent. NaCl solution. 

 Tben with the aid of scissors and forceps, the chitinous sheath, and the 

 eyes, are removed from the supra-oesophageal ganglion, and the specimen 

 removed to a watch-glass full of salt solution, wherein the tracheae and 

 muscles are removed. After a short time the object is placed for forty- 

 eight hours in Flemming's mixture, and then having been well washed, 

 the rest of the muscles and the fat are removed from the ganglion. It is 

 next put in 36 per cent, spirit, and gradually hardened. After dehydration 

 it is imbedded in paraffin. The sections were fixed down by Mayer's 

 method, and stained with a saturated watery solution of acid f uchsin. The 

 fixative used was Eabl's solution (chromo-formic acid and platinum 

 chloride). 



Treatment of Acari.f — Dr. C. Norner remarks that Acaridaa should be 

 treated according to their species and habitat. Such as live within a tissue, 

 e. g. the Aca7-us scahiei, are best obtained by softening the scabs in a 

 10 per cent, potash solution for an hour, or perhaps better by allowing a 

 weaker solution to act for a longer time. Very good results are produced 

 by soaking the scabs for a day in a dilute mixture of potash, glycerin, 

 water, and spirit. The mites are thereby rendered not too transparent 

 and preserve their form welL A very good preservine fluid consists of 

 equal parts of 90 per cent, spirit, glycerin, and water. When the scabs are 

 sufficiently softened, they are teased out in dilute glycerin under a dissecting 

 Microscope and all extraneous matter removed. Glycerin preparations 

 may be ringed round with turpentine, with red sealing-wax dissolved in 

 absolute alcohol or with gold size, &c. A good preparation should contain 

 mites in all stages of development, that is to say, eggs, larva, nympha, 

 male and female, and if possible the stage of exuviation. For such slides 

 glycerin jelly is a better mount than glycerin. The free-living mites and 

 ticks which infest the surface of their host are more easily obtained than 

 the pit-digging itch insect. The feather ticks of birds are almost as 

 numerous as the species of birds. These are obtained by laying feathers 

 under a dissecting Microscope and removing the animals with the needles ; 

 the breast feathers of small birds require to be placed in a dilute potash 

 solution from which they are picked out under the Microscope. The 

 histological structure of the Acaridse is best studied in the living animal 

 immersed in a drop of oil, glycerin, or water. The author has also used a 

 mixture of glycerin, spirit, acetic acid and eosin, where these reagents were 

 extremely dilute. To prevent the animals from being crushed during the 

 microscopical examination it is only necessary to support the cover-glass on 

 two others. 



Very pretty pictures may be obtained by staining : for his purposes 

 Eanvier's picrocarmine is the most generally useful. Other staining fluids 

 recommended are (1) a mixture of equal parts of picrocarmine and indigo- 

 carmine, (2) eosin either in alcoholic solution or watery, to which 1/3 

 glycerin is added ; (3) methyl-green ; (4) ammonia- carmine ; (5) Magdala 

 red. Kosanilin and fuchsin are the most suitable for the cast-off skin. 

 With regard to their receptivity for dyes it should be borne in mind that 

 mites are very uncertain , some taking up none or with great difficulty, while 



♦ Cuccato, G., 'Sulla struttura del ganglio sopra-esofageo di alcuni oitotteri,' 

 Bologna, 1887. t Zeitschr. f. Wiss. Mikr., iv. (1887) pp. 159-67. 



