304 ANNUAL OF SCIENTIFIC DISCOVERY. 



the whole quantity of dust examined, or even with the whole quan- 

 tity of organic matter, both eggs and spores may be said to be of 

 rare occurrence. We hare not in any instance detected dried ani- 

 malcules which were resuscitated by moisture, and when the dust has 

 been macerated in water none have appeared until several days 

 afterwards, until after a lapse of time when they would ordinarily 

 appear in any organic solution. 



Those who advocate the theory of spontaneous generation, on the 

 other hand, will doubtless find, in the experiments here recorded, ev- 

 idence in support of their views. While they admit that spores and 

 minute eggs are disseminated through the air, they assert that no 

 spores or eggs of any kind have been actually proved by experiment 

 to resist the prolonged action of boiling water. As regards Vibrios, 

 Bacteriums, Spirillums, etc., it has not yet been shown that they 

 have spores ; the existence of them is simply inferred from analogy. 

 It is certain that Vibrios are killed by being immersed in water, the 

 temperature of which does not exceed 200 Fah. We have found all 

 motion, except the Brownian, to cease even at 180 Fah. We have 

 also proved by several experiments that the spores of common mould 

 are killed both by being exposed to steam and by passing through 

 the heated tube used in the experiments described in this article. If, 

 on the one hand, it is urged that all organisms, in so far as the early 

 history of them is known, are derived from ova, and, therefore, from 

 analogy, we must ascribe a similar origin to these minute beings 

 whose early history we do not know, it may be urged with equal 

 force, on the other hand, that all ova and spores, in so far as we know 

 anything about them, are destroyed by prolonged boiling ; therefore 

 from analogy we are equally bound to infer that Vibrios, Bacteriums, 

 etc., could not have been derived from ova, since these would all have 

 been destroyed by the conditions to which they have been subjected. 

 The argument from analogy is as strong in the one case as in the 

 other. Sittiman's Journal. 



THE ARTIFICIAL PRODUCTION OF VARIETIES IN INSECTS. 



In a paper recently before the Entomological Society of Manches- 

 ter, Mr. Gregson made the following statements : 



After years of careful study of the habits and food of insects, I 

 determined to ascertain if a change of food would give a change of 

 coloring and marking to species liable to sport, and during the last 

 ten years I have been pursuing my experiments. The results of my 

 experience go to prove that most unquestionably many species, some 

 of them hitherto not often thought liable to vary, may be cultivated 

 into varieties. For instance, Bucephala, fed upon sycamore, is much 

 finer and darker than when fed upon any other food, though it is 

 well known that this species is never found upon that tree in its nat- 

 ural state. After enumerating many variations produced by changing 

 the food of the larva? of insects, the author stated : " What will per- 

 haps interest you most to know, and undoubtedly what I know best, 

 and have oftenest tried and succeeded in producing, is, that Arctia 

 caja, fed upon Petasites vulgare, or upon the common coltsfoot, will 

 produce darker specimens than when fed upon any other plant ; and 

 the chances are that when fed upon this food some of the specimens 



