INFORMATION TO CONTRIBUTORS 
The Proceedings is the official organ of the Academy for the publica- 
tion of brief accounts of important current researches of members of the 
Academy and of other American investigators, and for reports on the meet- 
ings and other activities of the Academy. Publication in the Proceedings 
will supplement, not replace, that in journals devoted to the special branches 
of science. The Proceedings will aim especially to secure prompt publication 
of original announcements of discoveries and wide circulation of the results 
of American research among investigators in other countries and in all 
branches of science. 
Articles should be brief, not to exceed 2500 words or 6 printed pages. 
Technical details of the work and long tables of data should be reserved for 
publication in special journals. But authors should be precise in making 
clear the new results and should give some record of the methods and data 
upon which they are based. The viewpoint should be comprehensive in giv- 
ing the relation of the paper to previous publications of the author or of 
others, and in exhibiting, where practicable, the significance of the work for 
other branches of science. 
Manuscripts should be prepared with a current number of the Proceed- 
ings as a model in matters of form, and should be typewritten in duplicate 
with double spacing, the author retaining one copy. Illustrations should be 
confined to text-figures of simple character, though more elaborate illustra- 
tions may be allowed in special instances to authors willing to pay for their 
preparation and insertion. Particular attention should be given to arranging 
tabular matter in a simple and concise manner. 
References to persons should include initials; citations of literature, 
numbered consecutively, should be placed at the end of the article; and short 
footnotes should be avoided. Indicate ^subject' for ^Contents'. 
Papers by members of the Academy may be sent to Edwm Bidwell 
Wilson, Managing Editor, Mass. Institute of Technology, Boston, Mass. 
Papers by non-members should be submitted through some member. 
Proof will be sent to authors only on their request, in order to avoid 
delay in publication. Authors are therefore requested to make final revisions 
on the typewritten manuscripts. The editors cannot undertake to do more 
than correct obvious minor errors. 
Reprints should be ordered at the time of submission of manuscript. 
They will be furnished to authors at cost, approximately as follows: 
Reprints of - - 2 pp. 4 pp. 6 pp 8 pp. Covers extra 
Charge for first 100 copies $1.00 $1.30 $2.20 $2.20 $2.00 
Charge for additional 100s .25 .45 .85 .85 .50 
INFORMATION TO SUBSCRIBERS 
Subscriptions at the rate of $5.00 per annum should be made payable 
to the National Academy of Sciences, and sent to Williams & Wilkins 
Company, Baltimore, or Arthur L. Day, Home Secretary, National Acad- 
emy of Sciences, Smithsonian Institution, Washington, D. C. Single num- 
bers, $0.50. 
Copyright^ iqij, by the National Academy of Sciences 
