238 ZOOLOGICAL PHILOSOPHY 



that all insects without exception are oviparous or sometimes apparently 

 viviparous, that worms are never found to appear on putrid meat, 

 except when flies have been able to deposit their eggs on it ; and lastly 

 that all animals, however imperfect they may be, themselves have the 

 power of reproducing and multiplying the individuals of their species. 



But unfortunately for the progress of knowledge we are nearly 

 always extreme in our opinions, as we are in our actions ; and it is 

 only too common for us to compass the destruction of an error, and then 

 throw ourselves into the opposite error. How many examples I might 

 cite in illustration, even in the present state of accredited opinions,^ 

 if such details were not foreign to my purpose ! 



It was thus proved that all animals without exception have the power 

 of reproducing themselves ; it was recognised that the insects and all 

 the animals of the later classes only do so by the method of sexual 

 generation ; bodies resembhng eggs had been seen in the worms and 

 radiarians ; and lastly the fact had been verified that the polyps re- 

 produce themselves by gemmae or kinds of buds. Hence the inference 

 was drawn that the direct generations attributed to nature never take 

 place, but that every living body springs from a similar individual 

 of its own species, by a generation that is either viviparous, oviparous 

 or even gemmiparous. 



This conclusion is erroneous in being too universal : for it excludes 

 the direct generations wrought by nature at the beginning of the animal 

 and vegetable scales, and perhaps also at the beginning of certain 

 _branches of those scales. Moreover, supposing that the bodies, in which 

 natiu:e has established life and organisation directly, obtain at the 

 same time the faculty of reproducing themselves, does it necessarily 

 follow that these bodies spring only from individuals like themselves ? 

 Unquestionably no ; and this is the mistake into which we have fallen^ 

 after recognising that of the ancients. 



Not only has it been impossible to demonstrate that the animals 

 with the simplest organisation, such as the infusorians and among 

 them especially Monas, and also the simplest plants such perhaps 

 as the Byssus of the first family of algae, have all sprung from indi- 

 viduals similar to themselves ; but moreover there are observations 

 which go to show that these extremely small and transparent animals 

 and plants, of gelatinous or mucilaginous substance, of very slight 

 coherence, curiously ephemeral, and as easily destroyed by environ- 

 mental changes as brought into existence, are unable to leave behind 

 them any permanent security for new generations. It is on the con- 

 trary far more probable that their new individuals are a direct result 

 of the powers and faculties of nature, and that they alone perhaps are 

 in this position. Hence we shall see that nature has played only an 



