2 : PROF. JULIUS MACLEOD ON TEN 
Carabus is longer than broad, and that this property is quite characteristie 
of the species under consideration. Measuring the length and the breadth 
of a dozen specimens, we find that the pronotum is always distinctly broader 
than long! The author of the description has been deceived by an optieal 
illusion, the system of curved lines which limit the pronotum producing a 
false appearance. 
Similar examples are to be found in thousands. Our method of describing 
animal and vegetable species has made little progress since the days of 
Lamarck and De Candolle. It is true our descriptions are more complete 
than in former times, attention being paid to characters which were unknown 
or neglected a century ago, but the way in which the characters are described 
has been little improved. The defects of the method are more seriously felt 
in proportion as the number of the known species becomes greater. 
The result of this state of things is that it is often very difficult—in fact, 
impossible—to identify a specimen, even by means of the best books. Again 
and again species already known to science are described afresh under new 
names, because it was impossible to recognize them in the previously pub- 
lished descriptions. 
Notwithstanding all this, the work accomplished by systematic botany and 
zoology is a very valuable one; tens of thousands of species have been 
exactly diseriminated, for the most part by a sort of instinct, which enables 
the experienced systematist to recognize the species by their facies. The 
masters of descriptive science possess this instinct to an astonishing degree. 
The difficulty begins when a specific description is to be made. 
Is it possible to adopt a better descriptive method, whieh would render 
the valuable knowledge collected by the systematists more exact, and make 
the inventory of living nature more useful? Is it possible to describe 
and to identify an animal or a vegetable species by means of numbers 
representing the values of the specific characters ? * 
Such a quantitative method is used for the description of inorganic objects. 
When we want to describe a specific mineral or a chemical substance (for 
instance, quartz, sea-salt, copper, sulphate, water, etc.), we measure a certain 
number of its properties, such as density, indea of refraction, coefficient of 
expansion, angles of the crystalline form, etc. The measurements are made 
according to certain conventions with reference to temperature, pressure, 
and other conditions of observation. The description consists of figures 
(so-called constants). 
* In deference to customary usage, I have used throughout the present communication 
the word “character ” in speaking of the various features the measurements of which give 
us specific differences. I should have preferred the term “property” as emphasizing the 
analogy between the specifie characters of living organisms and the various properties of 
inorganic objects. I hope to develop this point of view more fully in a subsequent 
publication. 
