A UTHORS INVES TIG A TIONS. 1 4 i 



closely identical in character with the artificially prepared infusions of hay, 

 and other vegetable substances, which are so speedily attended by their 

 myriad guests. Their purpose in life, as in the case of the animalcules 

 inhabiting artificial infusions, is to break down and convert into new 

 protoplasmic matter this otherwise waste product. To maintain the balance 

 here, however, and to check the too rapid increase of the herbivorous 

 monads, we find other types, such as Dinomonas and various Ciliata, 

 answering to the Carnivora among the various higher animal sub-kingdoms, 

 developed side by side with and feeding in turn upon the plant-eating 

 species. 



The general conclusions deducible from the long array of evidence now 

 produced with respect to the question of "spontaneous generation," or 

 " abiogenesis," may now be briefly summarized. From every line of inquiry 

 investigated, one and the same answer is invariably returned. Life in its 

 most humble and obscure form, be it existent as impalpable germinal dust 

 floating in the atmosphere, or shaken from a truss of hay, or manifested in 

 its more active state as the minute monads, bacteria, and other organisms 

 developed in infusions, tells everywhere the same unvarying tale. Traced 

 backwards to its origin, or forwards to its ultimate development, each 

 type is found by patient search to be derived, not de novo out of dead or 

 inorganic elements, but from a specific parental form identical in all respects 

 with itself, and whose life-cycle is as true and complete as that, even, of 

 man himself. 



To the scientific mind the conception that organic matter was primarily 

 eliminated, or in other words created, out of the inorganic, is forced home 

 as a natural and logical conclusion, and also that this transition may be a 

 process of every day occurrence. So far, however, as such recurring or de 

 novo generation is exhibited by the types of organic life dealt with in 

 this volume, or at present known, there is no longer left a loophole for 

 doubt. The evidence from all sides, revealed by the exhaustive light of 

 recent research, proves conclusively that in all these cases, down to the 

 lowest monad and bacterium, the reproduction of their kind, formerly 

 supposed to be altogether fortuitous and irregular, conforms in every essential 

 particular with that of the highest members of the organic series. 



Accepting, in point of fact, the infusorial or protozoic spore as the 

 physiological, though not morphological, equivalent of the ovum of all 

 higher animals, or Metazoa, Harvey's once famous, but since discarded, 

 aphorism " Onme vivum ex ovo,'' is found, so far as human knowledge has 

 as yet penetrated, to dominate with equal force from one extremity to the 

 other of nature's chain. To assert, however, that we have penetrated to 

 and laid bare the ultimate and finite confines of the organic realm, would 

 be an arrogant and altogether illogical assumption : a vast terra incog- 

 nita of organic forms may still remain to be explored. As yet, the latest 

 investigations of physiologists have pushed so far forward as to acquire an 

 approximate, though by no means exhaustive, knowledge of the " cellular " 



