1881.] 



MICROSCOPICAL JOURNAL. 



87 



careful reader will find nothing in the 

 article to which Dr. Detmers refers 

 (Vol. I, page 217), to justify such an 

 inference. On the contrary, the 

 value of any given angular aperture, 

 for any stated purpose, is capable of 

 accurate mathematical calculation — 

 it is no longer a matter of individual 

 opinion, which, in many cases, is of 

 little value. On the other hand, the 

 question of what objectives are the 

 best for common use is, so far as we 

 know, still purely a matter of experi- 

 ence ; and the work in which a per- 

 son is engaged will greatly influence 

 the decision. 



We are pleased to learn that Dr. 

 Detmers has succeeded in observing 

 the flagella referred to ; for although 

 others have doubtless seen them, this 

 is the first instance that has come to 

 our notice in this country. If we are 

 not mistaken, they were first observed 

 by Dr.\ Dallinger, with a Powell & 

 Lealand one-eighth. 



o 



Pasteur's Fluid. — Several per- 

 sons have requested us to give the 

 composition of Pasteur's fluid, which 

 was referred to last month in the re- 

 port of the Wellesley College Micro- 

 scopical Society. The fluid used by 

 M. Pasteur was a solution made 

 from the ash of yeast, but a very good 

 substitute, which is usually employed, 

 is composed as follows : — 



Potassic phosphate, . 20 parts. 

 Calcium sulphate, . 2 " 



Magnesic sulphate, . 2 



Ammonium tartrate, . 100 

 Cane Sugar, . . . 1,500 

 Water, 8,376 " 



10,000 



Clathrulina Elegans. — A short 

 time ago we found a number of speci- 

 mens of this beautiful Rhizopod in a 

 bottle of water in which Rotifers 

 were quite abundant. As the speci- 

 mens were larger than those described 

 by Prof. Leidy, we give the measure- 

 ments as they are noted in our book, 

 at the time : Diameter of capsule 43/^ 



~47-5^> diameter of stem i.g/', dia- 

 meter of openings in the capsule 

 7.25/^. The pseudopodia were con- 

 siderably longer than the diameter of 

 the capsule, very straight and clear. 



CORRESPONDENCE. 



To THE Editor : — In your November 

 number, in an article headed, " About 

 Objectives," the question is asked : " What 

 discoveries or new observations have you 

 made with your fine objectives ? " This 

 question I will answer. I have a y^ homo- 

 geneous immersion of R. B. Tolies, angle 

 of aperture, in medium of 1.535 refractive 

 index, 114'*. It has shown, with a Beck 

 No. 2 eye-piece, on Beck's best stand, 

 the flagella on bacterium termo, and 

 also flagella on the e.xceedingly small bi- 

 spherical Schizophytas, which constitute 

 the cause of swine plague. Has any low 

 angled Objective ever done that .-* Please 

 answer. 



The November number contains also 

 a report of a meeting of the Illinois 

 State Microscopical Society, in which I 

 showed a very thin section, cut with a 

 new section-cutter, made by W. H. Bul- 

 loch, and devised by Prof. Burrill, Mr. 

 Bulloch, and myself. Your report gives a 

 remark by Mr. Beck, who was present 

 and suggested (sneeringly .^) that some of 

 the surplus American ingenuity of the 

 members might advantageously be ex- 

 pended in inventing a section-cutter for 

 diatoms, Mr. Beck made the above re- 

 mark but for obvious reasons nobody 

 deemed it worth while to reply, and I 

 would not now, if his remark had not 

 been published. If Mr. Beck will kindly 

 furnish a knife that will cut silica it 

 will be a very small affair for American 

 surplus.ingenuity to invent a section-cutter 

 for diatoms, and to slice up Amphipleura 

 pellucida so fine, that Mr. Beck will have 

 difficulty to see the sections, unless he 

 uses American objectives. 



Very respectfully yours, 



H. J. Detmers. 



Chicago, Ills. 



To the Editor: — In your December 

 number, 1880, where I said that I had 

 " tried the new Gundlach ^^ with his j^^ 

 periscopic ocular, and got " good light and 

 fair definition " you made me say >^, in- 

 stead of " -^ " thinking, I suppose, that 



