22 Notes on some Microscopic Organisms. 
In reviewing tliis subject the following points would seem to 
be reasonably well settled. Objectives should be, and could be to a 
much greater extent than they now are, rated according to a uni- 
form standard. They should be named not arbitrarily, but in a 
manner indicative of their magnifying power. Ten inches is the 
standard distance of measurement in estimating powers. This dis- 
tance should be taken from the eye to the rule by which the mea- 
surements are made, without regard to the distance of the object 
on the stage. Magnifying power is always stated in linear measure. 
The magnifying pow er and angular aperture, as well as the maker’s 
name, should be engraved on all objectives, and added to all particu- 
larly important drawings made by their means. Oculars should be 
named, like the objectives, in such a manner as to indicate their 
magnifying powers or equivalent focal lengths. 
The following are some of the more important queries which 
still remain open. Should the standard 1-inch objective be cha- 
racterized by magnifying ten diameters as used in the compound 
microscope, or should it be compared to a simple lens of actually 
measured focus or foci? Should the objective be named by its 
equivalent focal length, or by its amplifying power, or both ? 
Should our standard distance of measurement be changed from 
10 inches (254 millimetres) to 9£ inches (250 millimetres) ? 
From what point in the objective shall the distance to the scale 
be measured ? At what point of screw-collar adjustment shall the 
objective be placed for rating its angular aperture and amplifying 
power ? Should the name ocular be substituted for “ eye-piece ” 
in general use ? — The American Naturalist. 
VI. — Notes on some Microscoptic Organisms. 
By Prof. A. M. Edwakds (U.S.A.) 
The following observations I desire to have recorded, the more 
especially as, from all I can learn, they are unique, or, at least, 
have not been seen and published by anyone else. At the same 
time, I wish now to place upon record some discoveries connected 
with the life-history of certain animal organisms of minute size 
which I consider of importance and throwing considerable light 
upon a rather obscure portion of Biology, namely, the so-called 
subject of “Spontaneous generation.” And I must say that I 
cannot but think that the use of this title, to designate the pheno- 
mena considered, is extremely inappropriate, and had best be 
discarded, as it does not properly indicate what is meant, and at the 
same time, I am sure, often prejudices persons in advance against 
