47 
valuable matter which it contains. A postscript is inclosed, extracts 
from which are here produced : 
P. $.—Since writing the above note, and before mailirg it, I have more carefully 
examined the plates of Diptera, and am satisfied that they are correct; correct also, 
so far as I have examined, in their minute details. 
As these plates already extend to twelve in number, in addition to the supplement- 
ary plate A and as all the families, I believe, are more or less fully represented, it 
appears to me that the benefit accruing to students from their immediate publica- 
tion more than outweighs any advartage which an additional plate could give, unless 
such plate could be prepared without delay. 
My idea is this: The plates now finished being so extensive and so near perfect, and 
their publication having been so long delayed, I should publish them as they are, or 
with such additions and corrections as you now have at your command, and leave it 
for a future edition, if such be called for, to make the work still more extensive and 
valuable. This is the way the thing strikes an outsider ; but perhaps you, who are 
‘behind the curtain, can see difficulties which others can not. * * * 
Permit me to refer to one serious inconvenience, not in the execution but in the ar- 
rangement of your figures. I mean the indiscriminate mixing, on the same plates, of 
insects of different families, so that the student wishing to identify a species by a ref- 
erence to the plates would not know to what part of the volume to turn. If he knew 
the name of the insect he can refer to it by means of the index; butif he do not know 
it he will not know in what part of the book to look for it. This will be most incon- 
venient in the Lepidoptera where the figures are scattered over somany pages. This 
was done apparently to economize space, and we shall have to submit to the incon- 
venience for the sake of the many benefits which we shall be able to derive from the 
work. 
September 25, 1873, Dr. Le Baron writes again as follows: 
I have looked through your valuable compendium of Diptera, and have made such 
suggestions and alterations as appeared to me desirable, and which I trust will meet 
with your approbation. As it was impossible to examine the work thoroughly, 
within the time allowed me, and in the intervals of other duties, I have confined my 
examination mostly to that important portion of the work which lies between pages 
92 and 180 of the manuscript. The introductory part, as I understand from the pre- 
face, was compiled in a great measure from notes furnished by Baron Osten Sacken, 
and therefore needs ne revision. Next follow the plates, which must be regarded as_ 
the special feature of the work. The figures are numerous, neat, pretty, and life-like, 
and I believe, in the main, correct. As many of them are copied from other authors, 
their accuracy will almost necessarily vary according to that of the respective au- 
thorities. Many of the figures are taken from Packard’s Guide, and many of those 
figures were prepared originally for the American Naturalist. I do not know who was 
the draughtsman, nor how correct they generally are, as I have never examined them 
in detail, But one of them which I have had occasion to examine recently, namely, 
that of Hypoderma bovis, on page 404, and which you have copied in Plate VIII, 21, 
is little other than a caricature, as you will see by comparing it with the original, or 
with Westwood’s Figure 3, Plate XIX of Walker’s British pee or with your own 
original figure of the text eal variety (VI, 37). 2 * 
And again, October 15, 1873: 
I have referred in several of my letters to the desirability of having a larger num- 
ber of copies of your work on Diptera struck off than you contemplated. The idea 
occurs to me that after 50 copies have been printed at yourown expense, an arrange- 
ment might be made with the Naturalists’ Company to print 1,000 or more additional 
copies at their expense on shares, they to have a part, perhaps a half, arising from 
their sale. 
