APPLICATION OF THE QUANTITATIVE METHOD 211 



of many plants are simply ignored or hardly mentioned.^ As 

 a consequence of the spirit of routine, microscopical characters 

 are still almost entirely excluded from the systematic descrip- 

 tion of Phanerogams, Vertebrate animals, shells, etc. Although 

 microscopes of modern type were brought into general use 

 between 1830 and 1840, at the time being many entomologists 

 have not yet realized that the descriptive work they are carry- 

 ing out without the microscope will have to be done over again. 

 By means of the method expounded in this book, it becomes 

 possible to describe exactly any primordium whatever, however 

 variable it may be. Using the microscope for the discovery and 

 the measurement of primordia we are enabled to go far beyond 

 the usual scheme. For the description of the higher forms of 

 life ^ there are practically no limits to the number of primordia 

 which may be used. (See p. 190.) Following the variation of 

 a given primordium through a long series of specific forms, inter- 

 esting and unsurmised resemblances and differences are dis- 

 covered. (See p. 68.) By means of tables of constants the 

 innumerable observed facts may be set in order. (See my paper 

 on Mnium.) Following this method we grow accustomed to 

 exactitude and we learn to use the terms with more accuracy. 

 Moreover, we find now and then that a given pecuUarity, which 

 was quite unknown and seems to be a futile detail, is a char- 

 acteristic feature of one species, with the consequence that a 

 decisive diagnosis of that species may be reduced to five or six 

 words with one or two numbers.^ 



§ 146.— IMPORTANCE OF SYSTEMATICS.— It would be 

 a mistake to disdain the work of the classic school. The talent 

 of observation of the masters of systematic science is marvellous. 

 They had exactly distinguished and classified an enormous 

 number of species with poor technical means, at a time when 

 optical instruments and laboratory science had not yet emerged 

 from childhood. They have been the pioneers of our science. 

 They were almost all enthusiastic collectors. Their collections 

 of objects have been collections of ideas : let us follow their 

 example. They were chiefly guided by a sort of instinct, which 

 enabled them to distinguish and to recognize the species by 

 their habitus (fades) . The high value of that instinct, acquired 

 and developed by experience, should be impressed upon the 

 mind of many modem biologists, who cannot realize how it is 

 possible, for instance, to recognize thirty or forty horticultural 

 sorts of Azalea indica by a glance at the plants without flowers. 



1 The study of the fruits and the seeds of exotic Angiosperms, and even of 

 many European species, is for the investigator an unlimited field full of promise. 



" And even for the description of many Thallophytcs and lower animals. 



' See my paper on Mnium, Table XXXIX. More examples will be given in 

 a paper on Grasses which I hope to edit later on. 



