RECORDS 515 



ters contain centrosomes and may progressively multiply by 

 division. Cytasters and centrosomes are formed also in enucle- 

 ated fragments obtained by shaking unfertilized eggs to pieces 

 before treatment by the magnesium solution, and these asters 

 may likewise multiply by division. 



These facts seem to leave no doubt of the formation of func- 

 tional centrosomes dc novo and independently of the nucleus. 

 Evidence was adduced to show that the asters may operate as 

 centres of cytoplasmic division, independently of the nucleus. It 

 was also shown that the magnesium eggs show numerous 

 gradation in the mitotic process between complete division and 

 partial mitosis. 



Francis E. Lloyd, 



Secretary. 



GEOLOGY AND MINERALOGY. 

 December 17, 1900. 



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



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

 proved. 



The following program was offered : 



E. 0. Hovey, Exhibition of Lantern Slides Illustrating 

 Some of the Quarternary Deposits of the Hudson River 

 Valley, and Some Miscellaneous Subjects. 



D. S. Martin, Notes on the Geology and Mineralogy of 

 THE Vicinity of Baltimore, Maryland. 



W. G. Levison, Minerals from the Jones' Fall Quarries, 

 near Baltimore, Maryland. 



Summary of Papers. 



Dr. E. 0. Hovey exhibited several series of slides on geolog- 

 ical subjects recently prepared by him for Professor Bickmore. 

 The first series illustrated the clay deposits of the Hudson River 

 Valley, and the process of manufacturing those clays into bricks ; 

 the second series comprised the outcrops of the Cortland series 



