28 



THE AMERICAN MONTHLY 



[February, 



the softer, flowing and granular inter- 

 nal portion, or endosarc, was unusu- 

 ally noticeable. It is always interest- 

 ing to watch the movements of an 

 Amoeba. No description of its move- 

 ments can enable one to form a cor- 

 rect idea of the appearance of the 

 living animal. The ectosarc is first 

 projected in the direction of move- 

 ment, then the soft endosarc flows 

 into the projected pseudopodium as 

 though into an empty space, the large 

 granules and foreign particles tumb- 

 ling about as freely as though sus- 

 pended in a watery fluid. In this way 

 the animal moves. We ask, wherein 

 is its vitality ? How can such a mass 

 of soft, transparent jelly manifest all 

 the phenomena of life, voluntary move- 

 ment, digestion, growth t It is a 

 deep mystery ; but there it is, under the 

 microscope, living, moving — an ele- 

 mental type of all life, the universal, 

 essential element of every living cell. 

 Watch it, study it carefully, think of 

 it, follow it through its life as an 

 Aniceba, then upward through the his- 

 tory of the whole living world, trace it 

 backward if you can, to its origin — 

 the primal germ of life. Then found 

 upon it a system of philosophy, and 

 what can it be but a perfect, consist- 

 ent philosophy of evolution ? 



All this from a single bottle of 

 water from a pond or road-side ditch, 

 in the dead of winter. 



Correction-adjustment for 

 Objectives. 



The subject of this article has 

 greater claims upon the attention of 

 persons who use the microscope as a 

 means of investigation than it has gen- 

 erally received. Whoever has occa- 

 sion to select a microscope without 

 knowing much about the instrument, 

 must experience great difficulty in de- 

 ciding what objectives he had better 

 get. He will find that a ^-inch objec- 



tive can be purchased for almost any 

 price from $14.00 up to $70.00. He 

 asks the advice of a practical micro- 

 scopist, who perhaps will tell him that a 

 good lens without an adjustment for 

 cover-glass will serve him just as well 

 as a more costly one with a collar ad- 

 justment. This seems satisfactory, 

 and, having duly considered the mat- 

 ter from that stand-point, he goes to 

 the optician, intending to act upon the ' 



advice thus given. But the optician 

 tells another story. "If a lens with- 

 out an adjustment is as good as one 

 having the collar, why is it that there 

 are so many who will pay several times 

 as much for the latter ? Here is a ^ 

 for $15.00, here is one for $35.00; 

 they are both the best of their kind, \ 

 yet my best customers prefer the " 

 $35.00 lens. It must be it is a much 

 better one for practical use." Now, 

 the argument of the dealer certainly 

 seems well-founded ; and the pur- 

 chaser is greatly confused by the ad- 

 vice of his friend and the practical 

 knowledge of the dealer. Is it possi- 

 ble to throw light upon such a con- 

 fusing subject ? We will endeavor to 

 give a few words of advice, partly 

 based upon experience, and partly 

 upon theoretical considerations. It 

 should be said at the outset that the 

 advice to be given in any particular 

 case, would primarily depend upon 

 what use is to be made of the objec- 

 tives. For microscopes are sold to 

 two classes of people : one class who 

 use them as a means of pleasure, or 

 recreation, and who find much satis- 

 faction in having objectives of sur- 

 passing excellence for the exhibition 

 of delicate test-objects ; another class 

 who use them in professional work, or 

 in investigations in histology, biology, 

 etc. The first-mentioned class would 

 requir'^- all the delicacy of adjustment 

 that the skill of the maker can devise. 

 By saying this, we do virtually ad- 

 mit that the collar-adjustment is of 

 value, and improves the quality of an 

 objective. Unquestionably it does; 

 but not to such an extent as would en- 

 hance the value of the objective for 



