7o8 



NATURE 



[February 26, 1920 



and the chemical activity of ions and non-ionised 

 molecules respectively. Communications on these and 

 other topics were afterwards read and discussed, 

 amongst the contributors or those taking part in the 

 discussion being Arrhenius (the originator of the 

 theory), Acree, McBain, Bousfield, Sand, Partington, 

 Porter, Newbery, Lindemann, Philip, and J. C. 

 Ghosh. 



Fundamental differences of opinion with regard to 

 the main problems discussed were very marked. The 

 evidence for the hydration of ions is by some held as 

 final, by others as having only a limited application, 

 and by yet others as quite inconclusive. Most attention 

 was given to the problem of the abnormality of strong 

 electrolytes. At extreme dilutions these electrolytes 

 are regarded by many as behaving normally, the 

 dissociation constant for uni-univalent electrolytes 

 being about 002, but owing to the magnitude of the 

 water-correction, and the difficulty of exactly fixing 

 the molar conductivity for infinite dilution, this result 

 must still be looked upon as uncertain. At ordinary 

 dilutions the law has no application, and the most 

 promising explanation is that elaborated by Dr. J. C. 

 Ghosh, who proceeds on the assumption that the 

 strong electrolytes are practically completely ionised 

 in all dilute solutions, but that there is an electro- 

 static equilibrium between mobile ions, which con- 

 tribute to the conductivity, etc., and inert ions, which 

 do not. .^n electrical dilution law is therefore sub- 

 stituted for the chemical mass-action law in the case 

 of strong electrolytes. For weak electrolytes this 

 electrical action would only enter as a negligible dis- 

 turbing factor of the mass-action law. The_ further 

 development of this idea may be awaited with interest. 



THE SPECIES CONCEPT AMONG FUNGI. 



IN the Transactions of the British Mycological 

 Society (vol. vi., part ii., September, 1919) Mr. 

 W. B. Bri'erlev protests against the practice of myco- 

 logists in describing as species the forms which are 

 presented to them in Nature or as pathological 

 growths, especially on cultivated plants. The descrip- 

 tion of new fungal species is based on the assumptions 

 that the distinguishing characters are of a morpho- 

 logical nature, and that the essential specific characters 

 are constant and hereditary and may be determined in 

 one specimen of one gener£»tion. But the laboratory 

 and field experience of the experimentalist shows that 

 under changes in the environment the whole structure 

 and facies of the organism may be transformed, while 

 under identical conditions there is considerable evidence 

 that the morphological variation of a particular fungus 

 is definite and constant. The so-called species of the 

 mycologist is comparable with the "ecad" of the eco- 

 logist, and is the resultant of the organism and its en- 

 vironment. "Ecads" indistinguishable from each other 

 may be produced from two distinct organisms- inter- 

 acting with one and the same environment, or with 

 two different environments. Two precisely similar fungi 

 growing on a potato and a decaying tree-stump respec- 

 tively may really be different species, though .the 

 systematic mycologist would consider them identical. 

 The true organism is a physiological equilibration, a 

 metabolic entity, the interaction of which with the 

 environment results in the prowth-form or "ecad." 

 It follows that the morphological species concept rnust 

 be given up in favour of the physiological species 

 concept. The only exact method of determining 

 species is by means of quantitative data derived from 

 cultural treatment under standardised physico-chemical 

 conditions, for this method alone reveals the physio- 



NO, 2626, VOL. 104] 



logical condition of the organism. The author sug- 

 gests that even the apparently stable forms of the 

 higher fungi. Agarics, Polypores, etc., are merely 

 "ecads," and that two precisely similar morphological 

 entities of, for instance, Agaricus tnelleus may con- 

 ceal totally different physiological constitutions which 

 under other conditions of growth would diverge 

 characteristically. 



Mr. Brierley also attacks another concept of mycology,, 

 namely, the " educability " of fungi, or the induction 

 by suitable treatment of permanent modifications in 

 their biochemical, morphological, or other properties. 

 This concept is widely held by microbiologists, but if 

 it implies a possibility of a change in the physiological 

 constitution of an organism, it follows that with fuller 

 knowledge and improved technique a rapid change of 

 one species into another is possible. The author 

 affirms that the condition of knowledge and the avail- 

 able evidence are not such as to warrant an hypothesis 

 so subversive of the foundations of biological science. 

 The presumed mutations may be due to the presende 

 of mixed populations in supposed pure cultures, or 

 merely the expression of a developmental stage 

 previously unrecognised ; further, no organism in 

 which sexuality exists or is conceivable must be used 

 unless its gametic constitution and genetic behaviour 

 under all the conditions of the experiment are known. 



THE UPPER LIMIT OF UNPLEASANT 

 BEATS. 



IT is well known that Helmholtz traced all dis- 

 cordant effects of two or more musical notes when 

 sounded together to the presence of beats occurring 

 between the prime tones, between the prime of one 

 and an upper partial of the other, between the upper 

 partials of each, or to beats occurring in some other 

 way. Further, to produce the unpleasantness in ques- 

 tion the beats must lie between certain limits of 

 frequency, which limits vary with the pitch in use. 



In this connection it is of interest to note that Mr. 

 Narendranath Chatterjee, of Chittagong, India, has 

 recently given a formula expressing the upper limiting 

 frequency for beats for which the roughness vanishes. 

 This formula he writes as follows : 



B=- 



N 



oy+n + z 



(I) 



where B is the number of beats per second for which 

 the roughness vanishes, N is the frequency of the 

 lower of the two tones sounded simultaneously, n is 

 the number of the musical scale containing N and 

 beginning with 32 per second as the fundamental of 

 the first scale (the octave of this beinp the funda- 

 mental of the next scale, and so on), and, finally, i is 

 the interval between N and the fundamental of the 

 scale in which it is contained. 

 Thus N, n, and i are connected by the equation 



N = 32 X 2"~' XI 



(2) 



The results of the law compared well with Mayer's 

 experimental values, as shown in the following table : 



Frequency B of beats when 



