MakrcH 8, 1912] 
As Darby infers, the Mississippi formerly 
flowed west of its present channel. It was 
separated from the Ohio by an interfluve, the 
remnants of which are the “ continuous ridge ” 
mentioned by Hall. By two successive cap- 
tures the Ohio diverted the Mississippi; the 
final capture led the Mississippi through its 
present gorge where the “ masses of limestone 
rock are seen on either side.” 
Henri Peyroux de la Condreniere, com- 
mandant at Ste. Genevieve from 1787 to 
1796, was a man of considerable scientific abil- 
ity. In one of his essays he maintains that 
the Great Lakes formerly discharged into the 
Mississippi by way of the Illinois River. He 
reasons that the valley is too wide and deep 
to have been eroded by the present Illinois 
River. Another reason quoted is not so well 
founded; the “vast alluvium” stretching 
along the Mississippi to the Gulf is also held 
to indicate a drainage from the Great Lakes. 
This conjecture is an interesting prelude to 
the work which has shown the extent and 
drainage of those great marginal glacial lakes 
that preceded the present Great Lakes. The 
quotation has been handed down by Bracken- 
ridge, the lawyer-traveler in his “ Recollec- 
tions of the West,” second edition, Philadel- 
phia, 1868 (page 241). He (Brackenridge) 
adds prophetically “At no distant day the 
labor and ingenuity of man will restore the 
connection between the Lakes and the Missis- 
sippi by means of an artificial channel.” 
F. V. EmMerrson 
UNIVERSITY OF MISSOURI 
SPECIAL ARTICLES 
HORNS IN SHEEP AS A TYPICAL SEX-LIMITED 
CHARACTER 
SEVERAL years ago Wood (1905) published 
a note in which he showed that, in a cross be- 
tween a Dorset Horn and a Suffolk (belong- 
Lowlands of Southeast Missouri,’’ University of 
Missouri Studies, Vol. I., No. 3, 1902. 
1 Joint contribution from the New Hampshire 
Agricultural Experiment Station and the Station 
for Experimental Evolution, Carnegie Institution 
of Washington. 
SCIENCE 
375 
ing to a hornless breed of sheep), the male 
offspring all developed horns but the female 
offspring remained hornless. He showed 
further that in the F, generation hornless 
males arise, and these do not carry the de- 
terminer for horns, and horned females, but 
only when they have the determiner duplex. 
Bateson (1909, p. 178) has discussed these 
facts and drawn the conclusion: “ Sex itself 
acts as a specific interference, stopping or in- 
hibiting the effects of a dominant factor, and 
it is not a little remarkable that the inhibi- 
tion occurs always, so far as we know, in the 
female, never in the male.” He admits, how- 
ever, the difficulty in distinguishing between 
this probability and the other possibility; viz., 
that the male provides a stimulating factor. 
Castle (1911, p. 102) concludes that the rea- 
son horns are more strongly developed in 
males than females is “the presence of the 
male sex-gland in the body, or rather prob- 
ably some substance given off into the blood 
from the sex gland, favoring growth of the 
horns”; and he adds that if the male Merino 
sheep (in which, usually, the male, and the 
male only is horned) is castrated early in life 
no horns are formed. He gives no reference 
for the last statement; and in view of the 
variability of the horned condition in the 
males of the “ Merinos” the conditions of the 
experiments would have to be carefully con- 
sidered before such a result could be accepted 
as settling the question of the dependence of 
horns in heterozygous males upon a secretion 
from the testis. 
The hypothesis that we have adopted and 
which works with entire satisfaction assumes, 
first, that, as in man so in sheep, the male is 
heterozygous (simplex) im sex. One sex- 
chromosome is then to be expected in the male, 
and substantially this condition has been 
found to hold for man by Guyer (1910). The 
female will then be duplex in respect to sex. 
One further assumption is necessary; there is 
an inhibitor to horn formation, and this is 
located on the sex chromosome; consequently 
it is simplex in the male and duplex in the 
female. Thus it belongs to the well-known 
class of sex-limited characters. The inhibi- 
