NOTES AND MEMORANDA. 145 



them in the dark, as the osmic acid in conjunction with chi'omic does 

 not undergo such rapid changes by light as when alone. In the case of 

 cochlea, young bones, &c., a further treatment with • 25 to • 5 per 

 cent, solution of chromic acid may be necessary for complete decalci- 

 fication. The object is then washed and placed in spirit, and the 

 sections may then either be examined in glycerine, or treated succes- 

 sively with absolute alcohol and turpentine, and then mounted in 

 Canada balsam. 



The great advantages of this fluid are its rapid hardening pro- 

 perties, and the fact that no further staining is necessary, the osmic 

 acid imparting sufficient colour to the cells, even when mounted in 

 balsam.* 



Microscopical Research under Difficulties. — Professor Eay Lan- 

 kester, writing to ' Nature,' f says that the following short preface 

 to a very valuable account of the stages of development from the 

 egg of one of the centipedes (GeopJdlus), no member of which group 

 had been studied previously to this account, gives so convincing a 

 picture of the enthusiasm for investigation which may animate the 

 modern naturalist, that he extracts it for the encouragement of the 

 " craft." 



Elias Metschnikoff has during the past fifteen years worked 

 more assiduously with the Microscoj)e at the observation of the 

 minute details of embryology than any other student. To him we 

 are indebted for our first accurate knowledge of this subject in the 

 case of many important animal forms, e. g. sponges, various jelly-fishes, 

 marine worms, the scorpion, and the book-scorpions, various insects, 

 crustaceans, starfishes, and ascidians. One result has been the injury 

 of his eye-sight. In his memoir on Geopliilus,t he says : — " After having 

 for many years sought in vain for material suited for the investigation 

 of the embryology of the centipedes, I chanced to obtain a quantity 

 of the eggs of Gcopliilm. My find, however, took place under such cir- 

 cumstances, and these interfered so much with my investigation, that 

 I feel justified in describing them more minutely. For some consi- 

 derable time I had been affiicted with a chronic affection of the eyes, 

 and consequently commenced in the spring of the present year a 

 journey to our south-eastern steppes in order to turn my attention to 

 anthropological studies. Instead of taking with me, as in previoi;s 

 years, all the ajjparatus necessary for microscopical research, I took 

 this time on my journey only anthropological measuring instruments. 

 When, then, I was in the neighbourhood of Manytsch, nearly in the 

 heart of the Kalmuk steppes, and was visiting a small forest planta- 

 tion, I discovered quite unexpectedly a number of eggs of Geo])kilus 

 which had been deposited under the bark of a rotten tree-stem where 

 the females were watching over them. I gathered up the precious 

 material, and having packed it carefully in two bottles, set off with all 



* A mixture of chromic and osmic acids for embryological purposes was 

 recommended by Dr. A. Milnes Marshall in ' Quart. Journ. Micr. Sci.,' N. S., 

 vol. xviii. (1878). 



t ' Nature,' vol. xix. (1879) p. 342. 



t ' Zeitschrift f. wiss. Zool.' (1875). 

 VOL. II. L 



