44 NATURAL SCIENCE. July, 



numbers for the first time, and who lack the patience or leisure to 

 acquire a grasp of the system on which they are based, are very 

 apt to be prejudiced against it, condemning it unheard as an artificial 

 and cumbrous device. 



The system consists in dividing the subjects on which books have 

 been written into classes and fixing a number to each. There are 

 ten main divisions ; each of these is subdivided into ten, and each of 

 these once more into ten, so that i,ooo so-called "sections" are 

 formed. The " Natural Sciences " (in the wide sense of the term) 

 occupy the sections, 500-599, whilst " Zoology " extends from 590 to 

 599, the several class-numbers being allocated thus : — 



590. General Zoology. 



591. Anatomy and Physiology. 



592. Invertebrata. 



593. Protozoa, Porifera, Coelenterata. 



594. Mollusca, Brachiopoda, Bryozoa, Tunicata. 



595. Articulata. 



596. Vertebrata. 



597. Pisces, Amphibia (Ichthyopsida). 



598. Reptilia, Aves (Sauropsida). 



599. Mammalia, 



By the use of decimals, these sections are further divided into 

 sub-sections to any degree of minuteness which may be desired ; for 

 instance, 595.3 is " Crustacea," subdivided thus : — 



595.31 Entomostraca. 



.32 Phyllopoda. 



.33 Ostracoda. 



.34 Copepoda. 



.35 Cirripedia. 



.36 Malacostraca. 



.37 Arthrostraca. 



.38 Thoracostraca. 



•39 Gigantostraca. 

 By the mere addition of decimal places, any one of these may be 

 divided and subdivided again, if at any time that be deemed 

 desirable. The insertion of the decimal point makes the proper order 

 of the divisions clear, and also makes it more easy for the eye to 

 catch the main class-number. There is no profound mystery in this 

 use of the decimal ; it is nothing more than a practical convenience. 



In order to indicate Geographical distribution, a series of numbers 

 has been allotted to the different divisions of the earth's surface : — 



.4 Europe. 



.41 Scotland, Ireland. 



.42 England. 



.43 Germany. 



&c. &c. 



.5 Asia. 



.6 Africa. 



.7 North America. 



.8 South America. 



.9 Oceania. 



