MICROSCOPIC PREPARATIONS OF INSECTs' EYES. 379 



A FEW Notes on Microscopic Preparations of Insects' 

 Eyes. By Henry N. Moseley, M.A. 



Good preparations which shall demonstrate clearly the 

 structure of insects' eyes are very much wanted in this 

 country, and, so far as I know, almost impossible to obtain ; 

 yet such are comparatively easy to prepare, and when well 

 made from objects not only admirable for class demonstration, 

 but also extremely beautiful in themselves. 



The eye of a large sphinx moth is most easily prepared, 

 best of all that of Acherontia atropos, but Sphinx ligustri 

 will do well. The moth should be killed, and the head 

 placed immediately in absolute alcohol. After it has been in 

 the alcohol about a week it should be taken out imbedded 

 in a mixture of oil and wax, which should be made rather 

 hard in order to offer plenty of resistance to displacement 

 when the chitinous parts are cut through. Sections may 

 now be made with ease in the same way as described for 

 Corti's organ, and the cut should be made from the convex 

 cornea towards the ganglion. The sections should be floated 

 on to slides, stained there with carmine, treated with absolute 

 alcohol, oil of cloves, and mounted in Dammar varnish or 

 Canada balsam, just as described for Corti's organ. The great 

 thing is to use plenty of absolute alcohol, and a thin-edged 

 hollowed-out razor. Sections thus prepared should show all 

 the structures in siM, just as given in Leydig's ' Tafeln zur 

 Vergleichenden Anatomic,' Tubingen, 1864. Such prepara- 

 tions as these display the general anatomical relations of the 

 several parts and their coarser structure admirably. The 

 finer structure of the nerve-fibres, crystalline bodies, &c., 

 described by Max Schultze, must be examined in small por- 

 tions of the organ, macerated in iodine serum or hardened with 

 osmic acid. Preparations of the eye of Dytiscus and other 

 insects may be obtained in the same manner as those of large 

 moths, but the hardness of the chitinous cornea renders the 

 cutting of sections very difficult, and I know of no reagent 

 which will soften the chitin without destroying the internal 

 nervous structures. If the heads of smaller moths be used, 

 sections, very instructive, may be prepared passing right 

 through both eyes and the cephalic ganglia. Preparations 

 of the eyes of mollusca, leeches, &c., may be prepared in the 

 same way as those of insects from specimens hardened in the 

 same manner in absolute alcohol. 



