ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 727 



piece is not used about one-half of that time is required. Of course 

 the time of exposure will vary somewhat according to the density or 

 transparency of the object, and if stained, according to the character 

 of the colouring matter." 



At a meeting of the Camden (U.S.A.) Microscopical Society,* Mr. 

 J. Carbutt took a negative from a spider's foot with a 2-inch objective 

 and an exposure of 2 minutes, and from a sheep's tick with an exposure 

 of 1^ minute, the shorter exposure being due to the object being much 

 less dense and yellow. " B " dry plates were used in both cases. 



Woodward's Photographs of Amphipleura and Pleurosigma — 

 It will be remembered that Dr. J. J. Woodward forwarded to the 

 Society, in illustration of papers by him,f fourteen photographs of 

 Amphipleura pellucida, and three of Pleurosigma angulatum. 



As these photographs are not generally accessible, it may be useful 

 to note that they were reproduced by a heliographic process (on a 

 scale of ^) in the ' Arch. f. Mikr. Anat.'J which is to be found in many 

 libraries in this country. The plates are accompanied by an abstract 

 of Dr. Woodward's papers by C. Janisch. 



Microscopical Examination of Handwriting. — Dr. J. H. Wythe, 

 of San Francisco, maintains, as we have already recorded,§ that every 

 man's handwriting is infallibly distinguished by three characteristics, 

 that may be detected by the Microscope while they escape the eye, 

 viz. : — rhythm of form, dependent on habit or organization ; rhythm 

 of progress, or the involuntary rhythm, seen as a wavy line or irregular 

 margin of the letters ; and rhythm of pressure, or alternation of light 

 and dark strokes. The proper microscopical examination of these three 

 rhythms, under a sufficient illumination of the letters, cannot fail, he 

 believes, to demonstrate the difference between a genuine and an 

 imitated signature. 



Professor D. T. Ames,|| while believing Dr. Wythe's views to be 

 sound, " prefers to more simply define the three characteristics as 

 habit of form, movement, and shade ; these, in connection with other 

 attendant peculiarities of handwriting, furnish a basis sufficient to 

 enable a skilful examiner of writing to demonstrate the identity of 

 any handwriting with a great degree of certainty. 



" In extreme cases, and especially skilfully forged signatures, the 

 aid of the Microscope will be necessary for a proper examination, 

 but for the greater proportion of cases of questioned handwriting a 

 common glass, magnifying from ten to twenty diameters, will serve 

 much the better purpose, as it is amply sufficient to reveal the 

 characteristics of the writing, while its greater convenience of use and 

 broader field of view are greatly in its favour. 



" In the writing of every adult are habits of form, movement, and 



* See 'The Microscope,' ii. (1882) pp. 43-4. 



t See this Journal, ii. (1S79) pp. 663-74, 675-6. 



% Arch. f. Mikr. Anat., xviii. (1SS0) pp. 260-70. 



§ See this Journal, i. (1881) p. 856. 



|| ' Penman's Art Journal.' See Anier. Journ. Micr., vi. (1881) p. 214. 



