66 NATURAL HISTORY 



Law of Priority 



In describing species it sometimes happened that more than one 

 person described the same form, giving it different names. In such 

 cases the name assigned by the one who first described it is used, the 

 second being considered a synonym. This is the reason for writing 

 the describer's name and date of pubHcation after the specific name. 

 Ordinarily the date and frequently the describer's name is omitted. 

 Thus the true daisy is properly Bellis perennis, Linn. 1758, or the 

 English sparrow, Passer domesticus, Linn. 



What Is a Species? 



We have taken a glimpse at the contributions of some of the con- 

 temporaries and near contemporaries of Linnaeus and have gained a 

 sHght concept of the problems these early workers faced in defining 

 and describing a species. Biological scientists of today are still 

 working on this problem. The principle involved is readily under- 

 stood when we look at a sheep, a cat, and a dog. One can easily sepa- 

 rate them from each other, various cats being put in one group and 

 diverse dogs in another. All domestic cats, whether they be the alley 

 variety or pet Persians, and all dogs, whether they be a "dog in the 

 manger" or "man's best friend," fall into well-marked and easily 

 separable groups, known as species. To continue further, one finds 

 in looking over representative mammals that many other species such 

 as the jaguars, ocelots, jaguarundis, and cougars, all have certain char- 

 acteristics in common with our domestic cats. These characteristics 

 are size, build, shape of head, nature of claws, teeth, and fur. The 

 zoological systematist, therefore, places them in one larger group or 

 genus which is called Felis, a relationship expressed below. 



Kingdom. Animal . Plarzb 



'Phylum - Onovdcdxx . Arthropod a. 'Koiltx£r<i.a.. eh=>. 

 Gla55 - "rlocmiTacxIioD , Pisces .Pept/ilia, Aves.cstc-. 

 Order"- Carpi vonx . 'R'ocCe-aticc.Chiroptera,ete- 

 Kimil/- PeUcLcce^ . <Zo.n idoe ."LCr^icCoca.etc. 



Genzxs . " feli^ . Lumhricus, eto. 



r 



-SpecieS- domesticcc.leo.tigTjs.eu^. 



Tndi vidical . lorn , ,Dick .Harry, etc. 



