CORRESPONDENCE. 
271 
that there are favourable times and conditions when the best work, 
obtained under ordinary conditions, may be surpassed ; and, further, 
that a very little gain in adjustments, quality of glass, illumination, 
&c., often presents the object, as it were, in a new light. It would, 
indeed, be wonderful if anyone had succeeded in meeting all the 
requirements and preserving the results in a photograph. I may 
still insist upon it, that his photographs of the diatom in question, 
however excellent they may be as compared with others, do not 
represent the best work of the best glasses under the most favourable 
conditions, and that, therefore, negative statements as to its structure, 
even when coming from so high an authority, are not so good as 
positive ones. Analogy would indicate that the structure of 
F, Saxonica (probably a variety of N. rliomhoides*) is the same as 
that of the large specimens of Navicula rJiomhoides. 
As to whether or not the diatom examined by me is the one 
generally known by the name of F. Saxonica, a few words may be 
necessary. I have long thought F. Saxonica to be only a variety of 
N. rJiomhoides. I have slides, and a fine gathering of material, con- 
taining three sizes of N. rJiomhoides, the largest easy for a dry ith, 
and the smallest not as difficult as the variety mounted by Moller, 
and called F. Saxonica. The only diatoms I have ever spoken of as 
F. Saxonica are those furnished by Moller, and about equal in difficulty 
of resolution, the No. 18 of his Probe-Platte, and if they differ from 
that at all, the difference is slight. 
As further evidence that the best work of the high-angle objectives 
has not yet been pJiotograpJied, it may not be out of place to say that 
the best photographic showing of the transverse markings of AmpJii- 
pleura pellucida that I have yet seen was obtained by Dr. Charles Jewett, 
of Brooklyn, with a Tolles' immersion ith, made four years ago, angle 
of aperture 115° at uncovered. 
I feel confident that none of us have yet seen the best work of our 
finest instruments. Much is to be gained by improved methods of 
illumination, patience, and " painstaking manipulations." We must, 
as was once remarked by Dr. Pigott, be sure that we are in best con- 
dition for work, and prepare ourselves for it. Then we should devote 
days to a study now passed off at a single sitting. 
Very truly yours, 
G. W. Morehouse. 
Errata in Dr. Johnstons Paper.! 
To the Editor of tlie ' Monthly Microscopical Journal.'' 
Baltimore, August 12, 1876. 
Sir, — Will you do me the favour to call attention to the following 
errata in my recent paper on the " Spermatozoa of Amphiuma " : On 
the first page, undulations instead of modulations ; formed for rounded. 
* See recent articles by Mr. Kitton, Professor Smith, and Mr. Stodder, in this 
Journal. 
t Tliese errors seem to be unpardonable, but if the reader saw Dr. Johnston's 
handwriting he would consider them very trifling indeed. — Ed. ' M. M. J.' 
VOL. XVI. U 
