THE WONDERS OF LIFE 



constant; on the contrary, many bacteria lose their 

 specific qualities by progressive culture under changed 

 food-conditions. By a change in the temperature and 

 the nutritive field in which a number of poisonous bac- 

 teria have been reared, or by the action of certain 

 chemicals, not only the growth and multiplication are 

 altered, but also the injurious effect they have on other 

 organisms by the generation of poisons. This poisonous 

 effect is weakened, and — what is most important — the 

 weakening is transmitted by heredity to the following 

 generations. On this is based the familiar process of 

 inoculation, an admirable example of the inheritance of 

 acquired characteristics. 



As the bacteria are still often described as "cleavage- 

 fungi" and classified along with the real fungi, we must 

 particularly point out the wide gulf that separates the 

 two groups. The real fungi (or mycetes) are metaphyta, 

 their multicellular body (thallus) forming a very char- 

 acteristic sort of tissue, the mycelium; this is composed 

 of a number of interlaced and interwoven threads (or 

 hyphens). Each fungus-thread consists of a row of 

 lengthened cells, which have a thin membrane and en- 

 close a number of small nuclei in the colorless plasm. 

 Moreover, the two sub-classes of the real fungi, the 

 ascomycetes and basimycetes, form peculiar fruit-bodies 

 which generate spores (ascodia and basidia). There is 

 no trace whatever of these real characteristics of the 

 true fungus in the bacteria. Nor is it less incorrect to 

 class them with the fungilli, the so-called unicellular 

 fungi or phycomycetes (ovomycetes and zygomycetes) ; 

 these form a special class of protists which has the closest 

 affinity to the gregarinae. 



Like the closely related chromacea, many of the bac- 

 teria show a marked tendency to form communities or 

 cell-colonies. These cell-communities arise, as else- 

 where, from the fact that the individuals, which multi- 



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