The Editor: Heredity and the Mind 
teach you better.’ An interesting ex- 
ample of this sort of teaching is furnished 
by Dr. Boris Sidis, lately professor of psy- 
chology at Harvard, whose feelings are 
outraged because geneticists have repre- 
sented that some forms of insanity are 
hereditary. He declaims for several 
pages‘ in this fashion. 
“The so-called scientific method of the 
eugenists is radically faulty, in spite of the 
rich display of colored plates, stained 
tables, glittering biological speculations, 
brilliant mathematical formulae and com- 
plicated statistical calculations. The eu- 
genists pile Ossa on Pelion of facts by the 
simple method of enumeration which 
Bacon and the thinkers coming after him 
have long ago condemned as puerile and 
futile. From the savage’s belief in sympa- 
thetic, imitative magic with its consequent 
superstitions, omens, and taboos down to 
the articles of faith and dogmas of the 
eugenists we find the same faulty, primi- 
tive thought, guided by the puerile, 
imbecile method of simple enumeration, 
and controlled by the wisdom of the 
logical post hoc, ergo propter hoc.” 
Now if resemblance between parent 
and offspring were, as Sidis supposes, 
the only evidence of inheritance of 
mental traits which the geneticist can 
produce, his case would indeed be weak. 
And it is perfectly true that “‘evidence”’ 
of this kind has sometimes been ad- 
vanced by geneticists who should have 
known better. 
But this is not the real evidence which 
genetics offers. The evidence is of 
numerous kinds, and several lines might 
be destroyed without impairing the 
validity of the remainder. It is impos- 
sible to review the whole body of 
evidence here, but some of the various 
kinds may be indicated, and samples 
given. The reader will then be able 
to form his own opinion as to whether 
4Sidis, Boris, M.A., Ph.D., M.D. Neurosis and Eugenics. 
Vol. XXI, No. 10, pp. 587-594, New York, October, 1915. 
457 
the geneticists’ proofs or the mere 
assurances of a few psychologists like 
Sidis are the more weighty. 
1. The analogy from breeding experi- 
ments. Tame rats, for instance, exhibit 
about as much life as a bag of meal; 
their offspring can be handled without 
a bit of trouble. The wild rat, on the 
other hand, is always ready to fight 
at the drop of the hat. 
Prof. W. E. Castle, of Harvard Uni- 
versity, writes:> “We have repeatedly 
mated tame female rats with wild 
males, the mothers being removed to 
isolated cages before the birth of the 
young. These young which had never 
seen or been near their father were very 
wild in disposition in every case. The 
observations of Yerkes on such rats 
raised by us indicates that their wildness 
was not quite as extreme as that of the 
pure wild rat but closely approached 
tha 
Who can suggest any plausible expla- 
nation of their conduct, save that they 
inherited a certain temperament from 
their sire? Yet the inheritance of 
temperament is one of the things which 
the psychologists most ‘view with 
alarm.”’ If itis proved in other animals, 
can we accept the psychologists’ declara- 
tion that it is wholly impossible in man? 
EVIDENCE FROM SEGREGATION 
2. The segregation of mental traits. 
When an insane, or epileptic, or feeble- 
minded person mates with a normal 
individual, in whose family no taint is 
found, the offspring (generally speaking) 
will all be mentally sound, even though 
one parent is affected. On the other 
hand, if two people from tainted 
stocks marry, although neither one may 
Medical Review of Reviews, 
Dr. Sidis’ article may be good medicine 
for the patients of the Sidis Psychotherapeutic Institute, Portsmouth, N. H., but it is not good 
science. How little he knows of elementary biology is revealed by an allusion (p. 591) to ‘‘some 
miraculous germ-plasm (chromatin) with wonderful dominant ‘units’ (chromosomes).’’ A college 
freshman in biology would be ashamed to think that chromosomes and hereditary unit characters 
are the same thing. A distinguished psychologist who does not know the difference, and who 
writes of ‘dominant chromosomes,” is hardly a competent critic of the facts of heredity. 
5 Dr. Sewall Wright called my attention to this critical evidence, and Dr. Castle furnished the 
details, in a letter dated August 4, 1916. He adds, ‘‘I am not satisfied that a clear statement can 
be made at the present time as to the inheritance in later generations. But my impression is, 
from handling large numbers of second generation rats, that there is little evidence of segregation 
and I am inclined to think that the inheritance is blending. As to the principal question which 
you raise whether temperament is inherited or not there is no doubt. The only question arises 
as to the precise manner of its inheritance.” 
