230 Transactions British Mycological Society. 



and genetic behaviour under all the conditions of the experi- 

 ment, be known. 



(4) Possible contamination by filterable gonidia must be 

 eliminated. 



(5) Adequate control experiments must be maintained (a 

 little matter, but one absolutely vital, which has escaped the 

 attention of many students of the lower organisms). 



Unless these five conditions are rigidly maintained in the 

 focus of one's attention, and exactly complied- with, the results 

 obtained in experimental studies on the educability of micro- 

 organisms can have but little value. 



Much of what has been said is drawn from bacteriological 

 investigation and few direct references to more strictly myco- 

 logical studies have been made. There are two reasons for 

 this. In the first place direct experimental work on the educa- 

 bility of fungi is confined to a very few investigations of which 

 more will be said later, and the criticisms and suggestions which 

 have been made apply equally both to bacteriological and 

 mycological studies. In the second place the concept of the 

 educability of micro-organisms had its birth in the laboratories 

 of bacteriology, and largely in the phenomena of the attenua- 

 tion of viruses of whose nature and organic composition nothing 

 is known*. Thence it has been taken over by mycologists and 

 applied to the fungi with a confidence and lack of critical 

 evaluation which is somewhat astonishing. 



Still, if this concept be true for the bacteria, it must also 

 be true for the fungi. The whole of biological science is founded 

 on the hypothesis that in their ultimate physiological constitu- 

 tion living organisms are constant, for otherwise it would be 

 futile to attempt even the most general systematic treatment 

 of individuals, which are the only forms in which the living 

 organisms are known to us. This concept cannot be true for 

 certain kinds of individuals and untrue for others, true for the 

 bacteria and untrue for the fungi, applicable to ferns, inapplic- 

 able to liverworts. Biological science stands or falls by the 

 truth of this concept, for without it there can be no systematised 

 knowledge of living things. 



A few words however may perhaps be said of the evidence 

 derived from fungal studies which has been regarded as 

 establishing this concept. The classical investigation is that 

 of Massee(25) in 1905 to which reference has already been made. 

 Even for that date this work was remarkable rather for what it 



* Whilst this paper is passirig through the press a stud}^ of acute infectiv-e 

 polyneuritis has appeared which is noteworthy as containing a description of 

 the minute organism composing the filterable virus causing this disease. 

 (Bradford, J. R., Bashford, E. F. and Wilson, J. A., Quart. Journ. Med., 12, 

 1919.) See also the same authors in the Lancet, No. 4979, 1919. 



