68 RECORDS 



Dr. Sumner described his further experiments upon the eggs 

 of Exocoetus, Salvelimis, Batrac/ms, and two species of Fitndii- 

 his. The methods employed were cautery and impalement with 

 glass needles. The results tended to prove that there is early 

 established in the embryo a definite region of growth, and that 

 the elongation of the body occurs through cell-multiplication in 

 this region. Additions from the germ-ring or other portions of 

 the blastoderm play at most a subordinate role. Destruction 

 of this region of growth led to cessation of embryo formation, 

 although the blastoderm continued to spread. On the contrary, 

 destruction at an early period of the entire embryonic sector of 

 the blastoderm was followed by the regeneration of a new 

 "embryonic shield." 



Henry E. Crampton, 



Secretary. 



SECTION OF GEOLOGY AND MINERALOGY. 



May 19, 1902. 



Section met at 8:15 P. M., Dr. A. A. Julien presiding. 



The minutes of the last meeting of Section were read and 

 approved. 



The following program was then offered : 



George E. Ashby, Some Inclusions in Mica and their 

 Relation to the Percussion Figure. 



George I. Finlay, Geological Observations along the 

 Northern Boundary of Montana. 



Summary of Papers. 



Mr. Ashby was able to show by a most interesting series 

 of specimens and lantern slides that definite geometrical rela- 

 tions exist between the percussion figures and the inclusions of 

 magnetite common in mica. The percussion figure often bisects 

 the same angle between the skeleton rays of magnetite. 



Mr. Finlay dealt with the stratigraphy and petrography of 

 the district along the 49th parallel of latitude west from the 

 great plains. The sedimentary series is of Algonkian argillite^ 



