50 
Katharine Foot and E. C. Strobell 
We have foiind it conveiiient to send lots of two dozen exposed plates 
to be developed and printed outside the laboratory. Our simple method 
of focussing having practically overcome the element of uncertainty in 
securing an accurate focus, we do not find it necessary to verify the 
focus of one negative before setting up another preparation. 
In series of photographs conveniently filed we have a most useful 
laboratory asset. In a few years, or even months, most preparations 
fade and are useless, whereas every good photograph is a record that 
is valuable for a life-time, transforming perishable preparations into 
practically imperishable records. 
We have now over three thousand photographs, representing thirteen 
different forms and a large proportion of these are of chroniosome groups 
in which every chromosonie is present. It is evident that such a Collec- 
tion is invaluable for exact comparison, compelling an appreciation of 
any Variation shown by the chromosomes at a given stage of develop- 
ment. Further, such variations are seen to be in keeping with variations 
in other cell structures, and this makes one very cautious in accepting 
theories that demand that such variations be set aside as pathological 
or artificial. 
The Photographie reproductions of this paper are bromide prints 
from our own negatives. We use this method of reproduction because 
we believe it is the only one that insures to the photograph the advantages 
that are claimed for it over other methods of illustration. The most 
important advantage claimed for the photograph over a drawing is the 
elimination of the personal equation, thus prohibiting the all unconscious 
accentuation of questionable detaüs, and preventing the giving to sonie 
structures a reality they do not possess, except in the brain of the sym- 
pathetic observer. This is impossible in an untouched photograph, but 
a method that can be raanipulated either in the print or the reproduction 
has no advantage over a drawing. Photographs can be attractively 
reproduced by the half tone method, but we abandoned the use of this 
method some years ago, because we found that in spite of every caution 
it is almost impossible to prevent the engraver from manipulating the 
copper plate. It is their custom to sharpen or soften details, as the 
case requires, and this practically reduces the scientific value of the 
photograph to the level of a drawing. 
Chromalin Nucleoli. 
One of the important points in which Euschistus crassus shows a 
marked Variation from other species of Etischisftis, is the presence of 
