86 RICHARDSON, ON STOPS FOR OBLIQUE ILLUMINATION. 
smaller organ did not escape the attention of Dujardin, and 
it was noticed by that naturalist as a character marked 
enough to separate this species from Ascaris, and to elevate 
it into a genus by itself. To this distinction I think we will 
be able to confirm its claim after our careful examination ; 
first, on account of its unequal spicula; second, from its 
rudimentary ccecal secreting appendages; thirdly, from the 
comparative indistinctness of its oral tubercles ; and so, follow- 
ing the great French helminthologist, I think we are justified 
in naming it Atractis dactyluris. 
I cannot close these remarks without taking the opportunity 
of recognising my obligation to Dr. John Barker for his in- 
valuable assistance in the course of my investigation, in veri- 
fying from independent observations almost all the results 
which I have tabulated in this paper. 
AppITIONAL Stop recommended for oblique illumination with 
the Acuromatic ConpEenseR. By B. Witis RicHarp- 
son, F.R.C.S8.I., Surgeon to the Adelaide Hospital, 
Dublin. 
In the January number of this Journal I drew the atten- 
tion of microscopists to some advantages which I had derived 
from the use of peculiar-shaped stops delineated 
in that communication. After my paper had been 
printed I further experimented on oblique illumi- 
nation with stops, one of which I found so par- 
ticularly useful that I have had the accompanying 
illustration made of it. : 
It might be thought that with this stop and high powers, 
such as the 1th and ~,th, the light would be too much inter- 
cepted. It is not so, however, for at the present moment I 
have before me the markings of P. Fasciola beautifully dis- 
played by it, and a 4th of T. Ross’s make. I can, therefore, 
also speak as highly of this stop as I did of those recom- 
mended in my last communication. In the short paper 
just referred to, 1 mentioned that at the time of writing it, 
the highest powers I had used with the stops were the 1th 
and 1th objectives. Since then, I have tried them with 
Nachet’s objective 7, which is equivalent to about the =,th 
of English makers, and have found that it performs excel- 
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