558 
PROCEEDINGS OF THE SOCIETT. 
gation. They are capable of adapting themselves to a wide range of 
conditions as regards the composition of the water. He (Dr. Talmage) 
had kept them alive for days in the lake water, diluted 25, 50, and 
even 75 per cent, with fresh water; and for periods varying from 8 to 
18 hours in fresh water only. 
Prof. Bell said a paper was read at the February meeting, in which 
Dr. W. B. Benham described a new earthworm from Central Africa 
under the name of Eminia equatorialis. It was found some time after- 
wards that the name Eminia had already been appropriated, Dr. Hartlaub, 
of Bremen, having given it to a bird previously found by Emin Pasha. 
In a letter received Dr. Benham proposed to alter the name given to the 
new earthworm to Eminodrilus. 
Prof. Bell also noted that after the last number of the Journal went 
to press, a letter was received from Mr. Pringle containing additional 
particulars with regard to the approaching Bacteriological Congress, and 
giving notice to intending exhibitors as to the conditions under which 
objects would be received. As might be supposed in anything which 
Mr. Pringle had to do with, a special feature was made of photography. 
Mr. Mayall said it would doubtless be remembered that at the last 
meeting of the Society Dr. Tan Heurck’s new Microscope was exhibited, 
and the design had been somewhat severely criticized. Having seen a 
report of what was then said, Dr. Van Heurck had written a rejoinder 
requesting that it might be read at the meeting : — 
“ I have just read in the ‘ English Mechanic * of May 29th, the 
criticism of the instrument which Messrs. Watson and Sons have con- 
structed to my specification. I appeal to your impartiality to allow me 
to refute the assertions made, and I trust you will authorize the reading 
of my reply. (1) Defect of the fine-adjustment. — Mr. Mayall wrongly 
compares the M atson system to Zentmayer’s. If the latter was defective, 
it was because it wanted a certain amount of play to work, as the small 
steel plate at the bottom, acting as a spring in the Zentmayer-Boss, was 
incapable of a quick action. It is not the same in Messrs. Watson’s 
instrument, on account of the tightening pieces which allow of remedying 
the wear and tear which inevitably results in every machine, whatever it 
be, after some time. Besides, in Watson’s system there is a strong 
counter-spring at the back coiled round a spindle having an action 
sufficiently strong to perfectly counter-balance the friction of the 
tightened sliding pieces. That the fixing of this fine-adjustment sliding 
between guide-pieces is not as bad as Mr. Mayall represents it, is also 
proved to me when I see that some other approved makers have adopted 
it for their best Microscopes, such as Messrs. B. and J. Beck, who, in 
their catalogue for 1890 declare this adjustment ‘ at once certain and 
decided.’ I have, moreover, had a long experience with Messrs. Watson’s 
system of fine-adjustment, and I know that when it gets out of order, 
which every fine-adjustment is liable to do in time, it can be put right 
in a few moments. This is not the case in several large Microscopes 
much praised. (2) The application of the fine-adjustment to the sub- 
stage is entirely defective, and seems even to prove, according to 
