10 
The President' s Address. By A. D. Michael. 
tion of mechanical means of cutting thin serial sections has so facili- 
tated many branches of biological research that the process has been 
almost universally adopted, and anatomists and embryologists are 
inclined to ask themselves how they ever got on at all without serial 
sections. From the inconvenience of having the series on several 
slides one wants to fill a slide almost from end to end, and thus, 
although an inch movement of a mechanical stage is sufficient in a 
direction transverse to the slide, yet practically at least 2J- inches are 
required in the direction of the length of the slide; although this 
may be roughly accomplished by merely slipping the slide along with 
the finger, yet this is an unsatisfactory process, as it is difficult to 
take the finger off without the slide altering a little, both as to 
position and focus, while non-mechanical stages are infinitely worse. 
Constructing an elaborate organ from a series of sections is a process 
requiring the most earnest attention, and stage difficulties in the way 
are a serious hindrance ; moreover, just when one is following the 
series most attentively the stage is apt to come against the sub-stage 
condenser and upset the illumination entirely. What is wanted is a 
smooth and fine working mechanical stage, with rectangular move- 
ments of 2^ inches by 1 inch, which has sufficient rigidity, will 
act as a finder, and which will not hit against the sub-stage con- 
denser. It is well worth an effort to attain this difficult but most 
desirable end. 
If we turn to what may be considered the other branch of activity 
of this Society, namely the work done by means of the Microscope, 
we at once find ourselves in the ocean. The time is past when the 
use of that instrument was practically confined to a limited number of 
experts; to-day it is the great working tool in the hanls of almost 
every student of biology ; the anatomist, the embryologist, the patho- 
logist, the botanist, the mineralogist, and many others use it alike ; 
and to review or summarize the work done with the Microscope would 
be as hopeless a task as to review that done with the pen or the knife. 
It was doubtless these considerations that caused one of your late 
Presidents to observe that in the future Presidents would be more and 
more forced to draw the subject-matter of their Addresses from those^ 
branches of science to which they respectively had paid special atten- 
tion. This has proved to be correct ; probably it is not altogether a 
disadvantage, for although it is reported that men who are really 
orators speak best when they have not anything whatever to talk 
about, yet plain men who are not orators are usually best worth 
listening to when they speak upon some subject with which they are 
well acquainted. Therefore you will probably anticipate that I shall 
address you upon that group of living creatures to which I have chiefly 
devoted my attention, namely the Acari ; and I have thought that it 
might perhaps be interesting to you if I shortly brought to your 
notice the progress that has been made in the study of these minute 
beings, not merely during the past year, but since Linnaeus first 
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