82 THE SCIENCE OF LIFE. 



root, and leaves. These include Fungi, Alga, and 

 Lichens. 



3.) ACROGENS. Plants which grow in height and not 

 in diameter. Liverworts, Mosses, and Ferns. 



4.) ENDOGENS. Vascular plants, in which the wood 

 and cellular tissue are mixed throughout, without dis- 

 tinct annual layers. The seed has but a single lobe, or 

 cotyledon. 



5.) EXOGENS. Vascular plants having distinct annual 

 layers of woody fibers, and radiations of tissue from the 

 medulla to the bark. The embryo has two seed-lobes, 

 or cotyledons. 



In the Animal Kingdom we have the following typical 

 forms, or subkingdoms : 



I. PROTOZOA. Simplest animal forms, being com- 

 posed of bioplasmic jelly. Monera, Gregarina y Rhizo- 

 pods, Infusoria, and Sponges. 



II. RADIATA. Radiate animals, which are subdivided 

 into I. CCELENTERATA, with distinct body-cavity, ten- 

 tacles, and nettling thread-cells. Hydrozoa, Anthozoa^ 

 Ctenophora. 2. ECHINODERMATA, with distinct aliment- 

 ary canal and nervous ring. Crinoids, Asteroids, Holo- 

 thurians, Echinoids. 



III. MOLLUSCA. Soft unsymmetric animals. Digest- 

 ive system developed. Nervous system irregular. Poly- 

 zoans, Tunicates, Brachiopods, Lamellibranckiates, Gaster- 

 opods, Cephalopods. 



IV. ARTICULATA. Nervous ventral cord double. 

 Limbs on same side as nerve-cords. Annelids, Crusta- 

 ceans, Arachnoids, Myriapods, Insects. 



V. VERTEBRATA. Double nervous system; one on 



