15 
II. — The President's Address: 
Sketches from the Anatomy of the Acarina. 
By A. D. Michael, F.L.S., &c. 
( Read 15 th January , 1896 .) 
Probably a man speaks best upon the subjects which have lately 
occupied his mind ; I have for this address selected that to which 
I have been devoting most attention during the last two years, 
namely, the anatomy of the Acari. It must be admitted that it is 
strictly microscopical, for the structure of creatures, amongst which a 
total length of two millimetres constitutes an exceedingly large 
species, must be entirely studied by means of the Microscope. One 
family, the Ixodidae, run considerably larger ; but they are the single 
exception ; in others, two millimetres would be a very rare length, 
and even one millimetre is large. The consequence of this minute 
size has been that very little has been known of the internal anatomy 
until late years ; even now there is probably no group of equally 
highly organised beings as to the anatomy of which less is generally 
known. Text-books are usually almost silent regarding it ; and what 
information is given is not always correct. Doubtless in the near 
future this will be corrected, as sources are rapidly accumulating 
whence reliable information on the subject may be drawn. The in- 
vestigation, however, is not entirely one of very recent years ; as early 
as 1812 we have Treviranus’ writings, not confined to the Acarina, 
but giving a good deal of information about them. In 1860-1 
Pagenstecker published his ‘ Anatomie der Mil ben,’ a much more 
ambitious work, beautifully illustrated, and dealing with the anatomy 
of Trombidium and of Ixodes, the former being a very good type. It 
is wonderful that Pagenstecker saw so much as he did with the 
means at his command ; perhaps his fault, if any, was that he saw too 
much, and was not contented to leave points which he was not able 
thoroughly to master to future investigators. This led him into 
some errors ; but what work is free from them ? Heller’s work on 
the anatomy of Ary as persicus in 1858, Gudden’s on Tyroglyphus in 
1861, and Furstenburg’s great work on the Itch-mites in the same 
year, may all be mentioned as substantial contributions to our know- 
ledge ; but the true modern research into the anatomy of these 
minute creatures may be considered to have begun with Oroneberg’s 
papers on the anatomy of Eylais extendens, which unfortunately is 
in the Russian language, and on the structure of Trombidium. 
Then followed Henking’s paper on Trombidium fuliginosum, pro- 
bably the best extant on the anatomy of any of the Acarina. These 
were followed by two papers of Nalepa’s on the anatomy of Tyrogly - 
phus in 1884 and 1885, and on that of Phytoptus in 1887. Two 
