196 THE AMERICAN MONTHLY [Jul 



size to hold the lamp-black together. Add the size drop 

 by drop from a lead pencil. After the lamp-black and 

 size are thoroughly mixed and worked up, add twenty-four 

 drops of turpentine and work up again, 



Radiolaria. — To the current issue of the journal of the 

 Quekett Club Mr. A. Earland contributes an interesting 

 article on the structure, distribution and life-history of 

 the Radiolaria, illustrated by three plates from the Re- 

 port on the Radiolaria of the "Challenger" Expedition. — 

 Knowledge. 



To kill Rotifers. — At a meeting of the Manchester 

 Society, Mr. M. L. Skyes contributed a note on the meth- 

 ods that Mr. C. F. Rousselet employs when preserving 

 and mounting organisms so that they shall retain their 

 natural forms with their colors, muscles, etc. Mr. Rousse- 

 let exhibited a number of microscopical preparations of 

 Rotatoria at the International Zoological Congress at 

 Cambridge, which claimed special notice for their beauty 

 and the success of the methods he had adopted. Rotifera 

 cannot be killed suddenly, by any known process without 

 contracting violently, and losing all their natural appear- 

 ance. To kill and preserve them with their cilia fully ex- 

 panded and in their natural condition Mr. Rousselet first 

 narcotizes them with a solution consisting of 3 parts of a 

 2 per cent solution of hydrochlorate of cocaine, 1 part of 

 methylated spirits, and 6 parts of water. The Rotifers 

 should first be isolated in a watch-glass and clean water, 

 and a drop or two drops of the solution added at first; af- 

 ter five or ten minutes another drop should be added, and 

 afterward drop by drop and very slowly until the animals 

 are completely narcotized. They may then be killed and 

 fixed by adding one drop of an eighth per cent to a 

 quarter per cent solution of osmic acid. To clear from the 

 solution they must be washed several times, and then trans- 

 ferred to a 2i per cent solution of formaldehyde, and 



