Account of a Filaria in a Horse’s Eye. 291 
peculiar haze or mist, loaded with a poisonous miasm) has slowly 
swept through the plantation, and stimulated the leaves of the hop 
to the morbid secretion of a saccharine and viscid juice, which 
while it injures the young shoots by exhaustion, renders them a 
favorite resort for this insect, and a cherishing nidus for the myri- 
ads of little dots that are its eggs. The latter are hatched within 
forty eight hours after their deposit, and succeeded by hosts of 
other eggs of the same kind; or, if the blight take place in an 
early part of the autumn, by hosts of the young insects produced 
viviparously, for, in different seasons of the year, the Aphis breeds 
both ways.”? The inference which Dr. Good deduces from these 
phenomena, is, that the atmosphere is freighted with myriads of 
insect eggs that elude our senses, and that such eggs when they 
meet with a proper bed are hatched in a few hours into a perfect 
form. In this manner, damp cellars are covered with Boletuses, 
Agarics, and other fungi, and walls and rocks with lichens and 
mosses. In these cases it is now fully ascertained, that the vegeta- 
ble is propagated by reproductive granules contained in the frond 
of the Alga, the spores of the higher Cryptogamia, the pileus, or 
cap of the Fungi, and the pollen of the anthers of the Phanero- 
gamia. 
_If we adopt the theory of spontaneous genenilion; we not only 
are obliged to adopt the hypothesis of the Archeus, to direct its 
Operations, but we shall be unable to account for the extinction 
of some races of organic beings; we shall be unable to explain 
the limitation of the characters of different genera and species, 
to certain defined limits ; and we shall equally be at a loss to ac- 
count for the notprodustion of new genera and species. Why 
is it, on this hypothesis, that each species is produced of nearly a 
certain uniform size, neither larger or smaller ? And why is not 
the whole mass of matter operated upon my this spiritus mundi, 
changed into organized beings ? 
Because we cannot, in many cases, actually detect the ova or 
germs, it by no means follows that they do not exist ; and be- 
cause we find a plant or an animal in some unusual habitat, we 
are not necessarily obliged to suppose that it could only have 
been brought into existence by spontaneous generation. It has 
been well observed, that “there are very few, if any, facts taken 
in support of the doctrine of equivocal generation, but what may 
as equally, and perhaps as justly, be used to support the contrary 
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