Ixxiv INTRODUCTION 



kinds : whence we get the various vessels and cavities of 

 the interior. Moreover, they deposit certain substances, 

 formed within them. These deposited substances begin to 

 accumulate in special places, giving rise to the formation of 

 organs. 



Lamarck held that spontaneous generation took place in 

 the way described above. He held that it still continues to 

 take place, wherever there happens to be lying about a 

 particle of matter of gelatinous or mucilaginous consistency, 

 suitable for vitalization by the ubiquitous invisible fluids. He 

 held that the organisms at the beginning of the animal and 

 vegetable scales are produced by spontaneous generation, 

 which as regards animals he was at first inclined to limit to the 

 infusorians, but subsequently extended to the worms. At first 

 the reproduction was by buds or gemmae ; subsequently it 

 became sexual. Lamarck regarded sexual fertilisation not as 

 the initiating point of development, but as a preliminary opera- 

 tion by which a gelatinous or mucilaginous particle of matter 

 was rendered fit for the reception of life. He considered that 

 it did not even confer life : the unfertilised ovum was not a 

 living thing, nor capable of " possessing life " : after fer- 

 tilisation, it was still not living, though now it had become 

 fit for Hfe. Life itself, he beHeved, was conferred by the 

 subsequent application of a gentle warmth of the nature of 

 incubation. This view naturally follows from the identifica- 

 tion of life with a movement of the contained fluids. 



It is not clear how Lamarck supposed that fertilisation 

 prepared the ovum for the reception of life. He conceived 

 that fertilisation consisted in the emanation of a " subtle 

 penetrating vapour " which escaped from the sperm and 

 penetrated the ovum. This " invisible flame or subtle and 

 expansive vapour " was the " aura vitalis," which Spallanzani 

 had long previously disproved. Spallanzani clothed a male 

 frog during cohabitation in a pair of trousers through which 

 subtle penetrating vapours could pass, but no organic matter : 

 no fertilisation was found to ensue. Spallanzani thus com- 

 pletely proved the materiality of the process of sexual 



