SCIENCE 



[N. S. Vol. XXXVIII. No. < 



enough, are not always considered by paleo- 

 botanists and stratigrapliers. 



It should be noted that my criticism was 

 limited to the inference that the evidence 

 from vertebrate paleontology as cited was con- 

 clusive in this problem. I have expressed no 

 opinion as to the validity of Dr. Peale's con- 

 clusions in regard to the age of the Judith 

 River fauna, chiefly because the subject is 

 under investigation and the evidence is not all 

 in yet. Mr. Barnum Brown has spent four or 

 five months of nearly every year from 1899 to 

 the present date, in collecting vertebrate and 

 other fossils for the American Museum from 

 the Lance, Hell Creek, Judith Eiver, Ojo 

 Alamo, Edmonton and Belly River beds, most 

 of which are or have been included under the 

 broad designation of the Laramie Group.' 

 He has secured a large amount of fine ma- 

 terial, made extensive observations on the 

 stratigraphy, and kept accurate records of the 

 location and level of his finds. Certain other 

 parts of the problem are under investigation 

 by Messrs. Granger and Sinclair in New 

 Mexico and Wyoming. Until these data have 

 been compared, studied and coordinated with 

 those previously published, it seems better to 

 retain an open mind in regard to the tenor of 

 the evidence from fossil vertebrates on the 

 Laramie question. 



W. D. Matthew 



American Museum of Natural History, 

 July 1, 1913 



MENDELIAN FACTORS 



To THE Editor of Science: The alternative 

 interpretation proposed by Dr. Henri Hus^ for 

 ratios found in F, crosses between sweet and 

 waxy varieties of maize, suggests the question 

 whether, we are to use Mendelian factors 

 merely as a form of notation to aid in the 

 orderly arrangement of certain facts of hered- 

 ity, or go further and insist that they have a 

 real existence. The observed ratio of 9 horny 

 seed, 3 waxy seed and 4 sweet seed was repre- 

 sented as resulting from the interaction of 



' Not in the Laramie formation as now limited 

 by the U. S. Geological Survey. 



= Science, June 20, 1913, p. 940. 



two factors, a factor 8 for sweet endosperm 

 and a factor X for waxy endosperm. The- 

 presence of both S and X was assumed to 

 result in horny endosperm. In the self-pol- 

 linated progeny of a sweet-waxy hybrid, both 

 S and X would be present in 9 out of every 

 16 seeds and this was the number of horny 

 seeds observed. X alone would occur in 3 out 

 of 16, the ratio in which the waxy seeds oc- 

 curred. S would also occur alone in 3 out of 

 16 seeds, but the number of sweet seed was 

 found to be 4 instead of 3 out of 16. On this 

 hypothesis, therefore, the one seed out of every 

 16 which would have neither X nor 8 was 

 included with the sweet seeds. 



Dr. Hus's proposed changes are in effect to 

 substitute W for our X, H for our 8, and tO' 

 add a common factor called S to all the mem- 

 bers involved. 



To the writer the only object in premising 

 factors at all is that by their use predictions 

 are made possible, and in the present case two 

 factors are adequate for this purpose. To as- 

 sume a third factor is like adding an unknown 

 constant to both sides of an equation. 



The test proposed by Dr. Hus for the reality 

 of the H factor is the same as one of the tests- 

 originally outlined as a test for the same fac- 

 tor which we called 8. What is needed to 

 prove the superiority of the formula proposed' 

 by Dr. Hus is some method of testing the 

 reality of the common basic factor. Until 

 some plant is discovered in which the basic- 

 character is absent there appears to be no way 

 of doing this. The presence of a factor can 

 neither be demonstrated nor disproven so long 

 as it is assumed to be universally present. 



When sweet and horny were the only alter- 

 native kinds of endosperm known the presence 

 and absence of a single factor was adequate to 

 make predictions regarding their behavior- 

 With the discovery of waxy endosperm it was 

 necessary to add a second symbol. But until 

 another form comes to light it is difficult to- 

 understand how a third symbol helps us to an 

 understanding of the inheritance of these 

 characters. 



If the symbols are taken to represent actual 

 entities it is of course anomalous to have a 



