6 CALIFORNIA STATE COMMISSION OF HORTICrLTrRE. 



SO fully as in the natural sciences; as a result, we have a perfect system 

 of classification, which enables us to recognize and study with the 

 greatest ease any natural object which conies under our observation. 



The earth naturally is divided into three great kingdoms — the min- 

 eral, the vegetable, and the animal. The mineral is the first and the 

 oldest. Without it, neither of the others could exist. In fact, the 

 vegetable and animal kingdoms may be considered as subordinate to 

 the mineral and springing from it, for the material part of all vegetable 

 and animal is mineral, and so soon as the vital element has departed, 

 the}' restore to the mineral what they have borrowed from it. The 

 vegetable kingdom comes next in order, for there could be no animal 

 life until there was abundant vegetable life to support it. 



Our business now is only with the animal kingdom, and with only 

 one branch, though a very important branch, of that. This kingdom 

 has been divided into two subkingdoms, known as the Vertebrata 

 and the Invertebrata. The Vertebrata include all animals having a 



d al ex 



FIG. 1. Diagram to express the fundaiiifutal structure of an Arthropod. 

 a, antenna; al, alimentary canal; 6, brain; d, dorsal vessel; ex, exo- 

 skeleton; ?, limb; ?!, nerve chain ; s, subesophageal ganglion. (After 

 Schmeil.) 



backbone, as mammals, birds, fishes, and reptiles. The Invertebrata 

 cover all that class of animals which have no backbone, or vertebra, 

 and this is by far the larger and more important branch of the animal 

 kingdom, as it includes a vastly greater number of forms and is more 

 numerous in its individuals than is the other. 



The Invertebrata have been divided into eight branches, as follows: 



Protozoa, which includes the lowest forms of animal life. These are 

 single-celled animals, many or most of them exceedingly minute, or even 

 microscopic in size, and without definite shape. In most cases repro- 

 duction is effected by subdivision. 



Poriferata, which are animals a stage higher in their development, 

 and including sponges and kindred forms. 



Ccelenteratn, in which we find the jelly-fishes and corals. 



Ecltinndermata , which includes the sea-eggs or sea-urchins and the 

 star-fishes, 



Vervies, which covers the various forms of worms, leeches, and their 

 kindred. 



Molluscoidea. This is confined to two groups of aquatic animals, the 

 Brachipoda and Polyzoa. The first of these was formerly placed in the 



