332 RECORDS. 



examination a zinc-blende'from Utah, the natural mineral vary- 

 ing in color from yellow to fawn and to pale brown. This was 

 the most intense tribo-luminescent substance that they had yet 

 investigated. Two bits one fourth the size of a pea, if pressed 

 together lightly with the fingers, caused a brilliant yellow-green 

 light to glow as long as the pressure lasted ; and it also pos- 

 sessed the property of becoming radio-responsive to the beta 

 and gamma rays of radium ; that it was the first natural zinc- 

 blende they had examined that showed this remarkable property. 

 Mr. W. J. Hammer showed a sample of artificial blende made 

 by Mr. W. S. Andrews, of Schenectady, N. Y., which gave 

 very strong tribo-luminescence. C. C. Trowbridge, 



Secretary. 



SECTION OF BIOLOGY. 

 April i i, 1904. 



Section met at 8:15 P. M., Professor Underwood presiding. 



The minutes of the last meeting of the Section were read and 

 approved. 



The following program was then offered : 



Gary N. Calkins, The Evidence of a Sexual Cycle in 

 Amceba Proteus. 



E. B. Wilson, The Cleavage-Mosaic in Patella. 



D. T. MacDougal, The Ecological Conditions in a Local 

 Desert in Lower California. 



Summary of Papers. 



Professor Calkins presented " The Evidence of a Sexual 

 Cycle in Amceba Proteus'' as shown by nuclear changes, includ- 

 ing the processes of mitosis and nuclear multiplication by 

 this method, the fragmentation of the multiple nuclei, the 

 mitotic division of the chromatin fragments, and the formation 

 of the secondary nuclei, and subsequent encystment of the 

 parent form. The entire process was regarded by the speaker 

 as indicating a series of changes leading up to the formation of 



