60 



NOTES AND CORRESPONDENCE. 



Atmospheric Micrography.— Under the above heading, there 

 appeared in No. XXII of the ' Microscopical Journal' the 

 translation of a paper by Professor Pouchet, of Rouen, pur- 

 porting to be the description of an instrument termed the 

 aeroscope, but which, at the same time, revived what some 

 might call the exploded theory of spontaneous generation. 



As it appears to me that this question cannot be said to be 

 finally disposed of, but as the learned professor's arguments 

 in favour of the theory are somewhat biassed, it may not be 

 inappropriate that the attention of microscopists should be 

 once more directed to the subject. 



By most advanced naturalists, the theory of spontaneous 

 generation has been discarded as absurd, or, at least, as highly 

 improbable, and mainly, I believe, on two distinct grounds, 

 viz. — 1st, tliat it is directly opposed to the accepted theory 

 that, for the production of a new individual, in either the 

 animal or vegetable kingdom, there must be a conjugation of 

 the ^' germ" and '' sperm" cells (pre-existent, therefore) ; 

 and 2dly, in consequence of the well-known experiment of 

 Professor Schultze with filtrated and unfiltrated air upon de- 

 composing animal substances.* 



Neither of these grounds suffices, however, for the final 

 rejection of the theory; for in a great many of the Protozoa 

 conjugation has never been traced, and, so far as they are 

 concerned, the sexual theory is, to some extent, hypothetical ; 

 and secondly, I do not recollect having read or heard that 

 Schultze's experiment has ever been confirmed by any English 

 or foreign microscopist or chemist of note, although the 

 complete confirmation of this experiment would effectually 

 dispose of the theory. 



Having thus given fair play to the advocates of the theory, 

 I shall now proceed briefly to examine Dr. Pouchet's argu- 

 ments in its favour. 



• See ' Carpenter ou the Microscope,' p. 485, &c. &c. 



