CONTENTS 
Page 
Preliminary Report upon the Possibility of Controlling the Land Slides 
Adjacent to the Panama Canal* 193 
Astronomy. — ^Discovery of Eight Variable Stellar Spectra ..... 
By Harlow Shapley 208 
Mathematics. — On the Linear Dependence of Functions of Several Vari- 
ables, AND Certain Completely Integrable Systems of Partial Differ- 
ENTLAL Equations By Gabriel M. Green 209 
Astronomy. — Systematic Motion among Stars of the Helium Type .... 
By Benjamin Boss 214 
Chemistry. — ^The Abundance of the Elements in Relation to the Hydrogen- 
Heltdm Structure of the Atoms By William D. Harkins 216 
Anthropology. — ^The Genetic Relations of Certain Forms in American Abo- , 
RIGINAL Art By Clark Wissler 224 
Astronomy. — The Situation in Regard to Rowland's Preliminary Table of 
Solar Spectrum Wave-Lengths By Charles E. St. John 226 
Astronomy. — Changes in the Form of the Nebula N. G. C. 2261 
By Edwin P. Hubble 230 
Zoology. — On the Effect of Removal of the Pronephros of the Amphibian 
Embryo By Ruth B. Howland 231 
Paleontology. — On the Presence of a Median Eye in Trelobites .... 
By Rudolph Ruedemann 234 
Botany. — The Nature of Mechanical Stimulation . . . TF. /. V. Osterhout 237 
Genetics. — ^Hereditary Reaction-System Relations— An Extension of Men- 
delian Concepts By R. E. Clausen and T. H. Goodspeed 240 
Mathematics. — Point Sets and Allied Cremona Groups (Part II) ... . 
By Arthur B. Coble 244 
Mathematics. — On a Theorem of Lucas . By M.B. Porter 247 
Mathematics. — ^Interpretation of the Simplest Integral Invariant of Pro- 
jective Geometry . By E. J. Wilczynski 248 
Genetics. — Size Inheritance in Guinea-Pig Crosses . . . ByW.E. Castle 252 
