Kathleen V. Ryley and Julia Bell 
423 
has been chiefly in the hands of the pure anatomist rather than in those of the 
student of philosophical evolution. The former has insisted on the importance of 
growth centres and anatomical unity of measurement ; he has usually no appre- 
ciation of the relatively high correlations of the parts of the bony structure. He 
is thus liable to overlook the fact that from the standpoint of evolution a complex 
anatomical organ may be of far more importance to the race and to the individual 
than one factor of it which may be an anatomical unity. In the second place 
Mendelism has become the mode, and to surmount difficulties about characters 
which do not " mendelise," it has been customary to assert that they consist of a 
complex of simple Mendelian units*. On the original Mendelian theory such 
'•' units" were asserted to be independent, although as such a theory was found to 
be unworkable, a crude theory of "coupling," as a measurable association of 
anatomically or physiologically simple unities, was evolved to cover the real facts of 
correlation. In this manner there has arisen a conscious or unconscious association 
of anatomical and Mendelian units, and it has been supposed that an anatomical 
unity would be more likely to "mendelise" than a combination of such unities — 
a single bone like the femur than a measurement like the leg length or the stature. 
The present result seems an illustration of the futility of neglecting the correlation 
of characters or treating them as compounded of independent Mendelian or even 
anatomical unities. The bridge of the nose consists of parts which are distinct 
anatomical unities, but the evolutionary factor is probably far better represented 
by the physiognomic factor — the whole bridge of the nose — than by any anatomical 
unit. When one part exceeds there is a correlated defect in the other part, and 
this rule extends practically through all the races examined. It is thus quite 
conceivable that a single measurement like the sagittal arc is from the evolu- 
tionary standpoint far more important than any of the simple arcs — opisthion to 
lambda, lambda to bregma, and bregma to nasion — into which we may reduce it by 
aiming at the measurement of anatomical unities. There is such a thing as an 
evolutionary factor, a determinant which controls the development of a whole 
series of anatomical unities, and the heredity brought into evidence by such 
a factor may be far more important from the standpoint of evolution than the 
heredity of any simple anatomical character. What group of anatomical units 
go to form any such determinant can only be appreciated by a thorough study of 
the correlations of simple anatomical parts. 
Especially in the nasal bridge is this matter of very great importance, for 
while within the race an individual with small maxillary height (D8 — 88) has a 
large simotic height (88), interracially this is no longer true, the race with a 
small maxillary height will have a small simotic height and the positive correla- 
tion interracially is very substantial (+ - 581) — this must be compared with the 
mean intraracial correlation which is — "333. Both these results are for males, for 
females the numbers are +"501 and —'226 respectively. This reversal of sign 
* Of course when it is convenient a vast congeries of factors, such as " Albinism " or " Jewishness, - ' 
are illogically treated as a simple Mendelian "unit" ! 
54—2 
