Sbptember 30, 1898.] 



SCIENCE. 



427 



as what are called species in speaking of 

 the higher plants, is a very pertinent ques- 

 tion. Any definition of species to be scien- 

 tifically accurate must in its essential points 

 apply to all plants and all animals and, if a 

 species of flowering plant is a perennial 

 succession of like individuals, it is hard to 

 see why in bacteria a perennial succession 

 of like individuals does not also constitute 

 a species. That the individuals in bacteria 

 are very different from the individuals in 

 flowering plants is certainly true, but that 

 does not affect the question of the validity 

 of the species in the former. As far as the 

 perpetuation of morphological likeness of 

 the individuals is concerned there is no 

 doubt that it is, to say the least, as com- 

 plete in bacteria as in flowering plants, and 

 the physiological constancy has been shown 

 by competent observers to persist in some 

 cases for hundreds of generations. That 

 these many generations have been produced 

 in months rather than in hundreds of years 

 does not, it seems to me, affect the case. 



When, therefore, the botanist denies that 

 physiological species are properly species 

 he is practically admitting that his own 

 definition, the perennial succession of like 

 individuals, is used by him in a special 

 sense, and he does not seem to be aware 

 that species as he limits them are artificial 

 and not natural. The belief that species 

 should be based on morphological rather 

 than physiological characters rests on the 

 assumption that the former are more likely 

 to be inherited and thus show the ancestry, 

 while the latter are more likely to be the re- 

 sult of the temporary attempts of the organ- 

 ism to adapt itself to the environment. It 

 is, perhaps, a question whether the grounds 

 for this belief are as valid as has been sup- 

 posed. We readily see morphological char- 

 acters which have been inherited, but it is 

 usually only by accident or experiment that 

 we recognize the physiological or patholog- 

 ical qualities. 



Let us turn for a moment from bactei'ia 

 to Saccharomycetes, whose characteristic 

 function is to invert and ferment the differ- 

 ent sugars. Here we have a group much 

 more limited in number of species than the 

 bacteria, but like them microscopic and 

 rapidly growing. Although not long ago 

 they were classified after a fashion on their 

 morphological characters, the admirable in- 

 vestigations of E. C. Hansen and his fol- 

 lowers have pointed out the important fact 

 that these characters, taken by themselves, 

 are less fixed, although the limits of their 

 variation may be fixed, than certain physio- 

 logical characters, such as the maximum 

 and minimum temperatures of growth, and 

 especially the temperature at which spore- 

 formation takes place. It is in these last- 

 named characters rather than in the former 

 that the specific distinctions in Saccharo- 

 mycetes are sought by those who study that 

 group specially. 



The same objection is urged by botanists 

 in this as in the case of bacteria that the 

 so called species are not species but races. 

 We naturally ask, races of what species? 

 There have been many attempts to deter- 

 mine the origin of the common Saccharomy- 

 cetes, and the question has been supposed 

 more than once to be settled. Without in- 

 tending to imply that the question is not 

 still open to investigation, I must admit 

 that there does not yet seem to be any sat- 

 isfactory proof to show from what higher 

 forms Saccharomycetes have been derived. 

 Although there can be no doubt that in the 

 germination of spores of certain fungi, es- 

 pecially the Ustilaginaccce, bodies are pro- 

 duced in abundance which not only closely 

 resemble Saccharomycetes in shape, but also, 

 in some cases at least, are capable of pro- 

 ducing alcoholic fermentation to a limited 

 extent, it does not seem to me that that is 

 by any means enough to warrant the opin- 

 ion expressed by Brefeld that the Saccharo- 

 mycetes are derived from and are degener- 



