230 



THE AMERICAN MONTHLY 



[December, 



A New Camera Lncida. 



The camera lucida is one of the most 

 valuable accessories the microscopist 

 who is doing original work can have. 

 It is true that man}^ investigators who 

 possess the faculty of drawing rapidly 

 and accurately without it, disparage 

 its use. By far the greater number, 

 however, recognize its value, and there 

 can be no question that drawings made, 

 or at least outlined, by its aid, are 

 more satisfactory to the scientific stu- 

 dent than those made by hand and eye 

 alone. For however accurately one 

 may attempt to delineate an object on 

 paper, if the outline is irregular and 

 complex — as in some species of 

 Micrasteritis for example, in which 

 every minute indentation requires to be 

 correctly shown in the drawing to make 

 it useful — the eye alone is not a per- 

 fectly reliable guide. Even though 

 the observer may be confident that his 

 drawing is correct in all its details, it 

 would be more satisfactory to others 

 if made with a camera lucida. It is 

 true that some distortion is produced 

 by the camera lucida, but the amount 

 is scarcely worth consideration with 

 ordinary objects. 



The Wollaston camera lucida has 

 long been in favor, and, so far as the 

 optical design is concerned, it is one 

 of the very best ; probably those who 

 are accustomed to using it will not 

 readily admit that there is anything 

 better to be obtained. It has the dis- 

 advantage, however, of requiring the 

 microscope to be placed horizontal, 

 which is frequently impossible and al- 

 ways inconvenient, while the eye must 

 be retained in one fixed position for 

 drawing. The latter condition is not 

 easily fulfilled without considerable 

 practice, and many persons — mostly 

 from lack of perseverance — declare 

 themselves unable to use the instru- 

 ment at all. 



Many other forms, which need not 

 be severally designated here, have 

 been devised which can be used with 

 the microscope vertical or inclined at 

 an angle. Of these we have found the 

 forms made by Mr. Grunow and Mr. 



Zeiss the most satisfactory, the former 

 having the advantage in projecting the 

 field of view further from the base of 

 the microscope. 



The new form which we now wi^h 

 to bring to the notice of our readers is 

 not yet in the market, but soon will be 

 placed on sale by Messrs. Ross & Co., 

 of London. In a short time we will 

 describe it, with the aid of an illustra- 

 tion, which is being prepared. As a 

 preliminary notice we may say that we 

 have had the opportunity of examining 

 the first one made, which was con- 

 structed to test the formula calculated 

 by Ur. Schroder for ?'Iessrs. Ross & 

 Co. We can unhe-^itatingly declare 

 that it is, in our opinion, the most per- 

 fect camera lucida yet devised. It 

 can be used with the microscope in- 

 clined at an angle of 45°, or, by using 

 an inclined support for the drawing 

 paper at one side of the microscope, 

 the latter may remain vertical while 

 drawing objects in fluid. The special 

 feature which distinguishes this camera 

 lucida is the surprising distinctness 

 with which the pencil can be seen in 

 drawing — not only is the pencil-point 

 clearly seen, but also the hand which 

 holds the pencil, and the whole field 

 of view is visible on the paper in a 

 fixed position, so that the eye may be 

 moved about without danger of losing 

 the proper position for drawing. 



Biolo*?ical Analogies in Animal 

 and Vegetable Life. 



At the Annual General Meeting of 

 the Quekett Microscopical Club, the 

 President, Dr. M. C. Cooke, delivered 

 the presidential address. We have 

 prepared the following summary of 

 the address from notes and from 

 memor\', but have not endeavored 

 to reproduce the language of the 

 speaker. The address will be printed 

 in a future number of the Society's 

 Journal. 



It is no longer possible, said the 

 speaker, to review, in the course pf an 

 annual address, the work of micro- 



