COXTKIBUTIOXS TO THE CYTOLOGY OF THE BACTERIA. 481 



Bacillopsis, are fill Fungi\, indicates of course nothing- 

 regarding the existence or non-existence of true Bacteria with 

 a typical vesicnlav nucleas. 



The vesicular nuclei described in Bacteria by Mencl (1904, 

 1005, 1907) and Rnvman and Kruis (1904) are, according to 

 Guilliermond (1907, 1P08, 1910), capable of a very different 

 interpretation. According to him, the ''nuclei" are really 

 nothing more than various stages in the formation of trans- 

 verse septa in dividing cells. This interpretation is vigorously 

 attacked by Mencl (1909), Avho maintains that vesicular 

 nuclei are actually present, and can be readily distinguished 

 frotji the transverse septa. Meucl's figures certainly seem 

 clear enough — as do the photogi'aphs of Kayman and Kruis. 

 And I find it difficult to believe that so accurate and ex- 

 perienced an observer as Mencl could make such a mistake. 

 Swellengrebel's (1907) results on B. bin ucleatum are also 

 favourable to his interpretations. Yet a certain amount of 

 uncertainty exists at present regarding these forms. 



Finally I must say that it seems to me probable that 

 Bacteria do exist which possess— at any rate during part of 

 their life-cycle — nuclei of the vesicular form chai'acteristic of 

 the cells of '" higlier '" animals and plauts. It is certainly not 

 le"-itimate to aro-ue that because Bacteria have not been 

 previously found which contain a vesicular nucleus, therefore 

 that any form in which a vesicular nucleus can be demonstrated 

 — e.g. Bact. gammari — does not belong to the Bacteria, 

 but to the Fungi or some other group. This is simply begging 

 the C|uestion. There is absolutely no reason, either from my 

 own observations or from those of other workers, why typical 

 vesicular nuclei should not occur in some Bacteria. The 

 evidence, in fact, is in favour of the view that such nuclei do 

 exist in certain Bacteria at certain stages in their lives. 



Variability of the Nucleus at different Periods in 

 the Life-cycle.^ — It will already be apparent to anyone who 

 lias read the preceding part of this paper, that the nucleus of 

 any given bacterium is not necessarily constant in its form at 



