May 17, 1912] 
the hybrid would be black or brown accord- 
ing as the factor N is or is not present. 
This factor, to which I have given the 
symbol N, and which is necessary to the 
production of both blue and black seed-coat 
colors, is, as already stated, one of the fac- 
tors for the production of anthocyan in the 
green tissues, and this was one of the rea- 
sons which led me to suspect that the blue 
pigment is a sap color. This same factor 
N is also one of those necessary for color 
in the flowers. But its importance in the 
economy of the plant does not seem to 
stop here. It may be merely a coincidence, 
but amongst about 4,500 third-generation 
plants grown in my experimental plots last 
year, this factor was present in every one 
of them that made even a fair yield of seed, 
except one strain of browns, and, with this 
exception, in those plants which lacked this 
factor the yield of seed was very meager. 
Furthermore, it is present in every stand- 
ard variety of cowpeas in this country, so 
far as I have observed, although many 
varieties have doubtless been produced that 
did not possess it. These facts would seem 
to indicate that this factor is in some way 
connected with vigor and vitality in the 
plant. 
Regarding the above colors, my breeding 
experiments led me to think that red, buff, 
brown and black were pigments related to 
melanin, and that blue was a sap color 
related to anthocyan. Dr. Albert Mann 
has made a study of this matter and has 
secured interesting and important results, 
which he will publish later. He kindly 
permits me to state that these surmises of 
mine were correct. I mention this fact to 
show that breeding experiments may be 
helpful to the chemist in investigating the 
chemical nature of these pigments. 
We now have before us some of the facts 
that so badly need interpretation. The 
case is not nearly so simple as this state- 
SCIENCE 
765 
ment of facts would indicate, for there are 
other important classes of facts that I have 
not considered because to do so adequately 
would require too much space. It is not 
surprising that such facts as these have led 
to much controversy. It is inevitable that 
the human mind shall attempt to compre- 
hend what it clearly apprehends, and hence 
that theories of various kinds should have 
been proposed to explain these facts. 
When we consider the fact that these fac- 
tors can be shuffled and recombined in every 
possible way, just as if they were concrete 
entities, each represented by an independ- 
ent morphological element in the germ 
plasm, it was to be expected that theories 
should be proposed involving such ele- 
ments. It is inevitable that this should 
have been the case. Such theories present 
a simple idea, easily grasped, leading to an 
almost absurdly simple scheme of symbols 
for portraying the facts of segregation and 
recombination. 
Some of these theories have gone so far 
beyond the present possibilities of investi- 
gation that many biologists, especially those 
only slightly familiar with the facts of 
Mendelism, have entered vigorous protests, 
and have even gone so far as to try to rule 
the facts themselves out of court. I wish 
to suggest to those who have not themselves 
conducted Mendelian studies, that it is well 
not to be too dogmatic about the facts in a 
field of investigation with which one is not 
very familiar. It would be a serious mat- 
ter to convince any one who has watched 
the shifting and recombining of these fac- 
tors that they are not real things. For one 
not thoroughly familiar with Mendelian 
phenomena to question the facts of segre- 
gation and recombination is as unseemly 
and unscientific a procedure as it would 
be for me to question the facts of physiolog- 
ical chemistry. The real trouble is not 
with the facts. It is with the interpreta- 
