Q2 MORPHOLOGY AND CULTURE OF MICROORGANISMS 



These conclusions are positive, but the species observed by Vej- 

 dowsky are not well-defined bacteria, and may be thought to belong 

 to the molds rather than to the bacteria. It has also been said, 

 not without reason, that Bad. gammari might be a yeast of the genus 

 Schizosacchromyces and that the filamentous bacterium studied by 

 Vejdowski seems to resemble a filamentous mold. 



However this may be, one of Vejdowsky's pupils, Mencl, has en- 

 deavored to apply these conclusions to other bacteria, which are well- 

 defined, notably B. megatherium, but has only succeeded in bringing 

 forth proofs which are much less convincing of the existence of a nucleus. 

 The author strived to discover a nucleus, but this organ ,is not constant 

 and does not show the structure of a true nucleus. 



Both Kruis and Rayman have discovered a nucleus in different 

 bacteria (B. myco'ides, radicosus, etc.). This nucleus appears only in 

 very young cells; it is not found in older cells, and seems (like the nucleus 



noted by Mencl) to represent merely the 



*, . [2tJ] t t <%^ incipient transverse septum which fixes 



I , 2 stains well at the beginning of its forma- 



** u, O ..., tion and in some ways resembles a nucleus. 



3 4 The studies of Penau, who also endea- 



FIG.^ 71. Bacillus megathc- vored to prove the existence of a typical 



rium. (After Penau.} i > 



nucleus in bacteria, were no more success- 

 ful. In B. megatherium, he describes the following phases. In the 

 youngest cells he observes a stage where the cytoplasm is very dense 

 and uniformly stained, without a trace of differentiation. Immediately 

 succeeding is a phase where the cytoplasm becomes less chromatic and is 

 filled with vacuoles. At this point the author finds in each cell a tiny 

 granule (Fig. 71, i), homogeneous and easily stained, situated at one of 

 the poles of the cell, very near the membrane. This granule he con- 

 siders to be a nucleus. Moreover, in the cytoplasmic web he observes 

 a series of stainable granules connected by slender trabeculae, thus 

 forming a kind of network which he likens to mitochondrial and chro- 

 midial formations. At the time of sporulation, Penau finds an in- 

 crease in the size of the nucleus (Fig. 71, 2 and 3) which changes to 

 a large granule; this is soon surrounded by a membrane and becomes 

 the spore (4), which is therefore formed mostly of chromatin. 



The same author discovers a very different structure in Bact. 

 anthracis. Here, after a stage of undifferentiated structure which 



