260 GENERATION. 



sion of the question was as energetic as it is now ; but the 

 positive advances in a knowledge of the generation of insects 

 has swept away the memory of such discussions, if they ex- 

 isted, as future advances may possibly cause many of the con- 

 troversial writings of the present day to pass into oblivion. 



For a time after the researches to which we have just al- 

 luded had taken their place in the history of science, there 

 was little written about spontaneous generation. Redi had 

 satifactorily described the mode of generation of many of the 

 entozoa, the origin of which had been obscure ; Harvey had 

 enunciated, in substance, his famous axiom " omne animal ex 

 ovo j " * Regnerus de Graaf had described, in the ovaries, the 

 vesicles which have since borne his name ; 8 and the knowl- 

 edge of ovulation and development began to make definite 

 progress, the important fact having been ascertained, that 

 viviparous, as well as oviparous animals, are produced from 

 ova. 



With the discovery, by Leeuwenhoek, 8 of living beings 

 in water, called by him animalcules, but since known as in- 

 fusoria, a new problem was presented to students of natural 

 history. Here were animal organisms, so small as to be in- 

 visible to the naked eye, existing in great variety and in infi- 

 nite numbers, the mode of generation of which was not un- 



1 HARVEY, Exercitationes de Generations Animalium, Londini, 1651. On page 

 2, is the following : " omnia omnino animalia, etiam vivipara, atque hominem 

 adeo ipsum ex ovo progigni." This quotation is from the original edition of 

 Harvey's work. In the life of Harvey, by Robert Willis, published in the Syd- 

 enham edition of the works, London, 1847, p. Ixix., is the following: "He an- 

 nounced the general truth : Omne animal ex ovo." It is probable that this is 

 the passage from which the familiar quotation is made. 



2 DE GRAAF, De Mulierum Organis Generationi inservientibits Tractatus No- 

 vus, Lugd. Batav., 1672, p. 177. On p. 181, is the following: "Ova in omni 

 animalium genere reperiri confidentur asserimus ; quandoquidem ea non tantum 

 in avibus, piscibus tarn oviparis quam viviparis ; sed etiam in quadrupedibus, ac 

 homine ipso evidentissime" conspiciantur." 



3 LEEUWENHOEK, Concerning little Animals by him observed in Rain- Well- 

 Sea- and Snow-water ; as also in water wherein Pepper had lain infused. Philo- 

 sophical Transactions, London, 1677, No. 133, p. 821, et seq. The observations 

 referred to were made in 1675. 



