96 
Maddox^ on Acari in a Nitrate of Silver Bath. 
N. indica is equally distributed^ while in N. prateocta it is 
irregular^ the granules being sometimes widely scattered. 
Then the termination of the marginal bands of strise are 
widely different in the two species ; and although a consider- 
able number of examples of iV. prceteocta have been examined, 
in no instance have the apices shown the slightest deviation 
from the oval or oblong outline. 
On the Generation 0/ Acari in a Nitrate of Silver Bath. 
By H. L. Maddox, M.D. 
(Communicated b}^ G. Shadbolt, Esq.) 
I VENTURE, through your indulgence, to offer the follow- 
ing remarks on a subject connected with both, photogra- 
phical and microscopical science, and trust they may not 
prove unacceptable. Very possibly others may have had 
their attention directed to the point in question, yet I am 
not aware of any observations concerning it having been 
published. Should you find me to be forestalled, may I beg 
you to append a notice of the same. 
In the early part of December a twenty-ounce nitrate of 
silver-bath, forty grains to the ounce, which had been in use 
during 1861, and placed for a month previous in a stoppered 
bottle, was returned to the bath and set aside in a cupboard, 
partitioned off in my working-room so as to convert it into 
a dark chamber. The bath, which is of cemented glass, 
covered outside with asphalt varnish, and kept in a v/ooden 
case with the cover shutting down over half its depth, re- 
mained unopened until the 12th of last month. When the 
solution was returned to the bath, half a sheet of white 
foolscap paper was first folded down on the top, and then 
the cover placed over it. The bottle was a perfectly clean 
one, kept to receive the nitrate bath when filtered, or when 
the sides of the bath were to be cleaned. The bath, after 
cleaning, was always washed out finally with boiled and 
filtered or simply filtered fresh-caught rain water — not out of 
the butt. I am thus particular in these details for reasons 
that will appear. 
Late on the afternoon of April 12th I moved the bath 
from the dark cupboard to the table in the room. On 
removing its cover, lifting off the paper, and looking along 
the surface of the liquid (as is my habit) to see if any scum 
be visible and remove the same by a little blotting paper 
wrapped round a strip of whalebone, I noticed on the surface 
