Some Concepts in Mycology. William B. Brierley. 229 



the contents of many cells which leave their empty cell walls 

 behind them." In addition there was observed "another 

 mode of interaction between the plasmatic substance in 

 bacteria cells. . .consisting in the direct union of two or more 

 individual cells. This 'conjunction' seems to be of no less 

 general occurrence than the process first mentioned." 



And these indications do not stand alone, for scattered through 

 the literature there are many sporadic observations which 

 point in the same direction. Without labouring this point 

 further it may be stated that if at any time sexual phenomena 

 be observed in the bacteria it involves the existence of hetero- 

 zygous individuals with the possibility of segregation on 

 Mendelian lines. Such segregation by the splitting up of a 

 heterozygote might explain the so-called "reverting mu- 

 tants "(50) in which the new form is described as constantly 

 giving rise to two types of colonies one similar to the obvious 

 parent and one like itself, the former breeding true, the latter 

 again shewing segregation. 



Whether or not these speculations contain any germs of 

 truth, the fact remains that we are in total ignorance of the 

 genetic constitution of a single bacterium, and this should 

 make one hesitate before elaborating theories of great import 

 which have their foundations in the processes of reproduction. 



Finally there is the imperative need to exclude all possibility 

 of contamination, or the "mutant" may merely represent an 

 invading organism. If, as would appear probable, many 

 bacteria may give rise to reproductive bodies so infinitesimally 

 small that they will pass through a porcelain filter, it will be 

 quite obvious that experimental technique must be very 

 considerably more exact and nice if the results are to be worthy 

 of serious consideration. 



From the brief sketch which has been given of certain of the 

 more important lines of research which bear upon the question 

 of the educability of fungi and bacteria it will be clear that much 

 of the evidence bears no relation to the point at issue, and that 

 of the remaining investigations scarcely one may be accepted 

 at its nominal value. 



There are certain evident minimal requirements for any 

 studies to this end which may perhaps be expressed as follows : 



(i) In order to ensure specific purity the organism must 

 be a single individual of a tested pedigree pure line. 



(2) The whole life-history of the organism together with 

 the range of its plasticity both morphological and physiological 

 must be accurately known in the minutest detail. 



(3) No organism in which sexuality exists or it is conceivable 

 that it may exist must be used unless its gametic constitution, 



