NOTES AND MEMORANDA. 
Dr. WILHELM Ktune, Professor of Physiology at Amster- 
dam, well known for his researches in histology as well as in 
physiological chemistry, has been appointed Professor of 
Physiology in the University of Heidelberg, as the successor 
of Professor Helmholtz, who has been called to a similar post 
at Berlin. 
Improvements in the Lenses of Microscopes.—For some 
time people in England have been content to let the im- 
provement of the optical powers of the microscope remain 
entirely in the hands of the makers, believing, apparently, 
that Mr. Lister had effected all in his suggestions and im- 
provements that could be desired. Dr. Royston Pigott, an 
able mathematician, formerly Fellow of St. Peter’s College, 
Cambridge, and a Doctor of Medicine of that University, 
was not, however, inclined to look at the matter in this way, 
and for many years has been working and experimenting 
with a view, first, to test the accuracy of our best object- 
glasses, and, secondly, to suggest means for their improvement. 
It should be remembered that Oberhaiiser, Nachet, and espe- 
cially Hartnack, on the Continent, not satisfied with the old 
system of combinations for object-glasses, and not having 
the benefit of Lister’s researches, have made excellent objec- 
tives on a totally different system, and during the last few 
years the last-named maker has carried his system of ‘‘im- 
mersion lenses” to such a point of excellence as really to 
surpass the best glasses on Lister’s system, in definition, 
penetration, working distance, and illumination. Those who 
do not admit the excellence of these objectives, which are 
now used by nearly all German histologists, have probably 
seen older glasses, made at a time when Hartnack had not 
reached his best. It is worth stating, now that the Parisian 
opticians are inaccessible, that Gundlach, of Berlin, has suc- 
ceeded in making excellent glasses of high power at astonish- 
ingly small prices, some of his 1-12ths and 1-l6ths im- 
mersion 1-16ths (so-called) being admirable in their perform- 
ance. They are not, however, equal to Hartnack’s glasses, 
which, though costing far less than what similar English 
