778 MICROSCOPY. j 
plate, from the lowest to the highest band, more satisfactorily than 
any objective I have hitherto tried. I must also give its perform- 
ance on Amphipleura pellucida by lamp light the preference over 
any similar work I have done or witnessed. The price of this 
objective was one hundred and seventy-five dollars. 
I send herewith some glass transparencies from negatives of the 
nineteenth band, takén by this lens, together with some paper 
prints of the several groups of the plate.—J. J. Woopwarp, 
Washington, Sept. 3d 
PHOTO-MECHANICAL Printinc.—In the September number of the 
Narturauist is an article under this caption, giving some of Dr. 
Woodward’s ideas, and an editorial dissent from them. Now this 
difference of opinion relates to a point that ought to be settled 
by the judgment of microscopists, and I write this for the pur- ' 
pose of calling for their views of the question. I quote from the 
article: ‘“ Even the microscopist himself, being unable to repre- 
sent all that he sees, is obliged to select what he conceives to be 
of importance, and thus represents his own theories rather than 
severe facts” (Dr. Woodward). The comment is [“ If, however, 
his theories are correct, and his delineation skilful, this very power 
of selection and construction enables him to give a distinctness 
and completeness which is lacked by the photographic camera.” ] 
Here are two almost opposite principles of illustration in ques- 
tion. Which should be the governing one? What is the object 
of the pictures? Obviously there are two; one for explanation 
of the observer’s theories; the other, that other observers may 
in repeating the observation be guided by and recognize what 
the first one had seen, and this I consider the all-important ob- 
ject of “figures.” If the observer draws only what he thinks im- 
portant, he must almost invariably make a picture quite differ- 
ent from the one seen in the microscope —he has omitted what 
he deemed the unimportant parts — and the pupil trying to fol- 
low him finds the actual appearance so different that he does not 
recognize it as the same. No doubt many of the misunderstand- 
ings or differences of opinions among microscopists have origi- 
nated from this very defect of published figures, which have been 
taken to be what they purported to be, representations of what 
was actually seen— “if his theories are correct;” but if his — 
theories are wrong then his skilful delineation has oe! misled 
