proceedings of the academy of [jan., 



January 13, 

 Mr. Arthur Erwin Brown, Vice-President, in the Chair. 

 Twelve persons present. 

 The death of Bushrod W. James, M.D., a member, was announced. 



January 20. 

 Mr. Arthur Erwin Brown, Vice-President, in the Chair. 

 Sixteen persons present. 



Papers under the following titles were presented for pubhcation : 

 "Myriapoda from Beulah, N. M./' by Ralph V. Chamberlain. 

 ''List of the Polycestid Gregarines of the United States," by 

 Howard Crawley. 



Preparation of Diatoms.— Mr. Frank J.Keeley called attention to a 

 method recently employed in studying the structure of diatoms, which 

 is supplementary to those previously described by him :— 



Mountino- broken valves on edge so as to obtain a sectional view, and 

 mounting in a manner that permitted of successively immersing the 

 forms in media of varying refraction indices. ■,• ci 



The present method consists in depositing on the diatoms a thm tiim 

 of silver, using the solution ordinarily employed for silvering mirrors, 

 which if dropped on the cover-glass containing the diatoms, will silver 

 the latter to a considerable extent before any appreciable quantity of the 

 metal i^ deposited on the glass. The finer the irregularities on the sur- 

 face the heavier will be the deposit of silver, and the best results are 

 obtained on gatherings containing broken and corroded forms, sepa- 

 rated plates "etc., the structure of which becomes quite apparent. 

 Thus conclusions can be drawn as to the correct nature of a complete 

 and perfect valve which will be more accurate than when it is itself 

 examined, particularly if the markings are fine, when they become 



filled with silver. . ■ , . i 



Under favorable conditions, after mounting m balsam and examining 

 bv transmitted light, valves or portions of them may be found having 

 the appearance of plates of perforated metal, and while the results so 

 far have principally been corroborative of those obtained by previous 

 methods some features not distinguishable under ordinary conditions 

 are rendered apparent, among which may be mentioned a ring of pro- 

 cesses near the margin of the valve of Coscinodiscus suhfilis, which 

 extends toward the interior of the frustule. , ■ -^r . . 



' The character of the raphe is particularly weU displayed in ^av^c^da 

 and its allies, as well as the small channels in the central and terminal 

 nodules, which doubtless have some function m connection with tlie 



