302 
adopt the view that one is dealing with minute 
parasitic forms. Some of the filterable viruses 
(pleuro-pneumonia of cattle, fowl pest, fowl 
diphtheria, epithelioma contagiosum and 
Novy’s rat disease) have been cultivated, so 
that the question as to whether we are dealing 
SCIENCE 
[N. S. Vou. XLVIII. No. 1238 
realize Osborn’s* “hypothetical chemical pre- 
cellular stages”; they lie somewhere in the 
scheme between simple colloidal and more 
complex cellular states like bacteria. Some 
thirty-two or thirty-three disease-producing 
filterable viruses are now known to exist, so it 
TABLE SUMMARIZING CHARACTERS OF POLYHEDRAL VIRUS OF INSECTS 
1. Cultivation of virus 
2. Filtration of virus 
3. Examination of virus with ultra-microscope. 
4, Effect of heating on virus when suspended in 
water 
5. Effect of dry heat on virus 
6. Effeet of drying on virus at room temperature. 
7. Effect of glycerine on virus 
8. Effect of direct sunlight on virus when dry 
9. Effect of putrefaction on virus 
10. Effect of alcohol on virus 
11. Effect of carbolie acid on virus 
12. Effect of virus on 1 per cent. sugar solutions 
13. Effect of virus on methylene blue and sodium 
nitrate solutions 
14. Effect of virus on gelatin and casein 
with organisms or not is solely an academic 
one. We are justified at present, however, in 
not classifying such viruses either with the 
plants or animals. 
The table gives a summary of the chief char- 
acters of the wilt virus. The virus used in 
these tests was prepared from diseased gipsy 
moth, army worm and tent caterpillars. That 
proteins like gelatin and casein are not af- 
fected when treated with the filtrate in which 
the virus has been concentrated by centrifug- 
ing is curious because insect tissue is com- 
pletely emulsified through the action of the 
wilt virus. This action is therefore probably 
a cytolytic one due to the action of toxins and 
is not caused by the elaboration of a proteo- 
lytic enzyme on the part of the virus. 
In a physico-chemical explanation of the 
origin of organisms on our planet the filterable 
viruses seem to be of considerable interest and 
I do not understand why they seem to be so 
persistently neglected by all writers on the evo- 
lution of life. The filterable viruses probably 
Has not been cultivated 
Passes through Berkefeld ‘‘N’’ but not through 
Pasteur-Chamberland filter 
Nothing visible that could be interpreted as being 
different from minute protein or pigment par- 
ticles 
Destroyed at 60° C. in 20 minutes 
Destroyed at 70° C. to 80° C. in 20 minutes 
Resistant for 2 years 
Resists 98 per cent. for 6 months 
Resistant for 12 hours 
Resistant for an indefinite time 
Destroyed by 80 per cent. in 15 minutes 
Destroyed by 5 per cent. in 3 weeks. 
No growth, no fermentation 
No growth, no reduction 
No growth, no liquefaction 
is reasonable to assume that the earth, water 
and atmosphere are full of non-parasitie forms 
which we have no means of recognizing at 
present. 
R. W. GuasEr 
Bussry INSTITUTION, 
HARVARD UNIVERSITY 
s‘*The Origin and Evolution of Life,’’ by 
Henry Fairfield Osborn, Charles Scribner’s Sons, 
New York, 1917, p. 80. 
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