NOTES AND MEMORANDA. 163 



Another Method of Staining. — Dr. A. Lang of the Zoological 

 Station at Naples, having been occupied with the difficult histology 

 of the Turbellaria, and particularly with the nerve-systems of these 

 and other groups of flat worms, found that the method hitherto 

 in use of staining the nerve-tissues was not satisfactory in all 

 respects. It seemed to him to be most desirable to colour distinctly, 

 in the nerve-system, not only the nucleus and the nucleolus, but also 

 the vessels and the protoplasm of the ganglia. Many Dendrocoela 

 with thick basilar membrane proved to be almost totally impervious 

 to distinct colouring. To overcome this difficulty he made several 

 experiments, and found the following mixture (which must of course 

 vary with the nature of the object to be stained) to be beyond 

 expectation : — 



50 parts 1 per cent, picro-camiine. 



50 parts 2 per cent, eosin (aqueous solution). 



The objects, previously hardened in alcohol, are left in the 

 mixture ^ to 4 days, according to their size and their facility of 

 imbibing the colour. Then comes the alcoholic treatment, which is 

 as follows. The picrin is extracted by 70 per cent, alcohol, which 

 must be frequently changed. Then 90 per cent, and absolute alcohol 

 is added, the latter so long as any eosin is dissolved. In imbedding 

 in paraffin the copious use of creasote is much to be recommended. 



Dendrocoela stained in this way showed, on making sections, the 

 most distinct colouring he ever obtained, and that for every part, but 

 especially the nerve-system. Nucleus and nucleolus, glands, adipose 

 tissues, &c., appear nearly carmine red, all the rest eosin red.* 



Size of Society Screw and of Slides. — At a recent meeting of 

 the State Microscopical Society of Illinois, Mr. Bulloch urged the 

 desirability of adopting a uniform objective screw of larger size than 

 the Society screw now in use, as being essential to the efficacy of low- 

 power lenses of high angle. That the Society screw which has now 

 become an almost indispensable convenience, is too small to admit of 

 efficient work from these lenses, is (says the ' American Natui'alist f) 

 a conceded fact, and some makers in the United States who make low 

 powers of enormous angle, have already adopted special screws for 

 them. The uniformity urged by Mr. Bulloch is greatly to be desired 

 and could be easily attained if its importance were appreciated in 

 time. 



In an article upon the preparation of rocks and fossils for micro- 

 scopical examination by E. Fritz Gaertner, in the April number of 

 the ' American Naturalist ' for 1878, the advantages of slides measuring 

 25 X 45 mm., over those 3.x 1 inch, were stated to be as follows: — 

 (1) They can be rotated on the stage, (2) they are less liable to 

 break if dropped, (3) they take up less room. It was also stated that 

 this size was adopted by the New York State Museum of Natural 

 History, and by lithologists and palaeontologists generally, both in 

 Europe and America. These arguments seemed to Mr. S. H. Grage 



* ' Zoologiseher Anzeiger,' vol. ii. p. 45. 



t 'American Naturalist,' vol. xiii. (1S79) p. 60. 



M 2 



