394 TRANSACTIONS OF THE [dEC. 20, 



The egg of Arenicola affords evidence in favor of the view 

 that the astral rays and spindle-fibers are mei'ely temporary con- 

 ditions of the cytoplasm and that they ma}^ arise and disappear 

 as often as certain processes in the cell begin or cease. They 

 appear to be simpl}' the expression of an activity. It is also 

 shown that strnctures which are in themselves indistinguishable 

 from astral rays may arise as the result of processes absolutely 

 unconnected with karyokinesis. 



A fuller discussion of these and other questions is deferred to 

 a later paper. 



Hull Zoological Laboratory, University of Chicago, 



November, 1897. 



Stated Meeting. 



December 20th, 189t. 



The Academy met with President Stevenson in the Chair. 

 14 persons present. There being no Academ}^ business at the 

 last meeting, the reading of the minutes was omitted. Mr. 

 "William G. DeWitt, 88 Nassau street, was nominated as resident 

 member, and referred to the Council. The Section of Geology 

 and Mineralogy then organized. 



The first paper of the evening was by Mr. Arthur Hollick, en- 

 titled " Recent Explorations for Prehistoric Implements in the 

 Trenton Gravels." Dr. Hollick described the deposits seen in 

 section at Trenton, N. J., during the last summer, and the ma- 

 terials taken from the pit b}' himself and the other members of 

 the special committee of scientists investigating Trenton gravels 

 during the early summer of 1897. He described the character- 

 istics of the deposits, the position of the artefacts in the gravels, 

 and summarized the conclusions that may be drawn from their 

 occurrence. A fuller account has already appeared in Science 

 for November 5th, 1897. The paper was discussed bj' Professor 

 Stevenson, Dr. Julien and Professor Martin. The second paper 

 of the evening was by Professor Kemp, entitled "Some Eruptive 

 Rocks from the Black Hills." Professor Kemp summarized the 

 geological features and structure of the Black Hills and asso- 



