Spontaneous Generation. 145 



it is established that living forms do not now arise 

 in dead matter. And, by the study of the forms 

 themselves, it is proved that, like all the more com- 

 plex forms above them, they arise in parental prod- 

 ucts. The law is as ever, only that which is liv- 

 ing can give origin to that which lives," omne vivum 

 ex vivo. For the particulars of his observations I 

 refer you to his lecture, " Researches on the origin 

 and life-histories of the least and lowest living 

 things," in the scientific journal, Nature, October 

 23 and 30, 1884. 



160. This then is the first way, that of cultivat- 

 ing a special germ. Another way is that 2 b - Ob 

 of following these organisms while they yatiou in 

 are out in their own line of life, and Nature * 

 watching them in their natural conditions. In 

 these conditions, a number of forms are found to- 

 gether, as Ehrenberg observed; or they work con- 

 secutively on a given material, as Dr. Dallinger de- 

 scribes. I can but refer you again to the instruct- 

 ive account which this latter observer made the 

 subject of his address, on retiring from the presi- 

 dency of the Royal Microscopical Society, last 

 spring. It may be found in the Scientific American 

 Supplement, April 28, 1888. His subject was re- 

 stricted to those organisms which do that special 

 work of fermentation, called putrefaction or decay. 

 But his conclusions cover the whole ground before 

 us. There are putrefactive organisms resembling 

 in form those other microbes which are parasitic 



