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 oihex fiingi, 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 AlgfE, 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 generation, 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 non-production 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 by 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 



