SIGNIFICANT ACCURACY IN RECORDING GENETIC DATA 213 
organs, they have assumed that no precautions whatever were taken 
to eHminate environmental differences. Since the statement was 
made that plants were grown under diverse conditions, a fact men- 
tioned merely in connection with the question of the effect of stimuli 
on corolla size, they seem to have concluded unjustly and unreasonably 
that the data from these experiments were used in the paper under 
consideration. 
On the other hand, Goodspeed and Clausen are perfectly justified 
in asking for a description of the way in which my data were taken. 
I wish to make such a statement, therefore, in order to support my 
former paper and some other studies on the inheritance of flower size 
which are to be published in the near future, and because of the op- 
portunity presented to illustrate a question of considerable general 
interest. This question, which as a teacher of genetics I have found 
neglected by research students more than any other, is: What is sig- 
nificant accuracy in recording data? 
The seemingly opposed statements of Goodspeed and Clausen 
and of myself serve to illustrate the thought in mind. The two 
allegations are not wholly discordant. Although I do not wish to 
withdraw or to modify my own statements, at the same time I am 
willing, in a broad sense, to accept most of their conclusions. Ex- 
cluding certain differences in our data that are undoubtedly due to 
dissimilar conditions at Berkeley, California, and at Boston, Massa- 
chusetts, my own results are similar to theirs except as to the magni- 
tude of the changes caused by environmental differences. The point 
upon which we differ decidedly is the significance of the results in 
relation to the problem at hand — the inheritance of differences in 
corolla size in Nicotiana. 
One of my college instructors once said to me: "It is seldom 
necessary, in the interests of scientific accuracy, to weigh a ton of 
hay on an analytical balance." That statement might be made the 
basis of a course on Precision of Measurements. One is hardly ever 
required to impress mechanical accuracy upon really earnest students. 
They will weigh and measure material with the utmost pains (in spirit 
at least). What is difficult is to impress an idea of true precision. 
It is not uncommon to see measurements recorded to tenth milli- 
meters after the random use of two scales having a one percent differ- 
ence, or material for analysis weighed to the fourth decimal place 
with weights that have never visited the Bureau of Standards, on a 
