THE LAW OF PRIORITY 515 



adopted by the scientists of the entire world. One of the basic 

 rules formulated by this commission is the Law of Priority. This 

 has to do with the scientific name each animal and plant is to 

 bear. Suppose an unfamiliar microscopic animal is observed. The 

 scientist draws it, photographs it, perhaps he kills it, and studies 

 it as stained and sectioned material. He then consults the de- 

 scriptive classification organized since 1895 and seeks the proper 

 place to catalog his specimen. If the specimen is not similar to 

 any known organism, the scientist gives it a generic and specific 

 name, writes a description, and publishes his findings. If no 

 other scientist reading his paper has ever come across it or seen 

 a description of it elsewhere, this scientist is thereafter credited 

 with the discovery. He has added a new creature to the list of 

 known organisms. 



Crustacea 



The phylum Arthropoda is subdivided into five present-day classes. There are many fossil 

 arthropods, some of which are quite unlike present-day forms. 



The method of the classification of to-day. All living things are 

 placed into one of two kingdoms, the plant kingdom or the ani- 



