APPENDIX B. xxiii 



an organism may pass, more or less rapidly, through the 

 Bacterium and the Vibrio phase and grow into a Leptothrix 

 thread, which, in its turn — by further growth and develop- 

 ment — may give rise to a microscopic fungus producing 

 large and definite ' spores/ These fungus-spores, under 

 similar influences, are capable of developing at once into 

 a mycelium similar to that from which they have been 

 produced. They do not again go through the lower terms 

 of the series, but are veritable spores, serving only immedi- 

 ately to reproduce a fungus. On the other hand, it is an 

 undoubted fact, which, although often stated, is not generally 

 known or admitted, that Torula-^^^ and other fungus- 

 germs may also originate as minutest visible specks of living 

 matter which, instead of passing through the stages of Bac- 

 terium^ Vibrio, Leptothrix, grow and develop at once into 

 fungus-spores, previous to the formation of a fungus-mycelium. 

 There is, indeed, strong reason for believing that the 

 spores and confervoid-looking filaments in question have not 

 dropped as such from the atmosphere, but that they are, 

 rather, living units which have developed within the crystals. 

 It is almost impossible not to be struck with the impro- 

 bability of the former of these alternatives, when we take 

 into account the number of such large spores and filaments 

 which, by this supposition, would require to have been 

 present in the atmosphere over the crystallizing materials, as 

 compared with the extremely limited number of such large 

 organisms, which have ever been obtainable when experi- 

 mental observations have been made upon the nature of the 

 solid particles existing in the air of all ordinary localities \ 

 The best evidence in proof of the view that they are pro- 

 ducts of a development which has taken place within the 

 crystal would be obtained, if it could be shown that in a given 



^ In all my investigations I have never met with spores exactly 

 similar to these, except in one or other of the ammoniacal solutions. 



