4 INANIMATE AND ANIMATED NATURE. 



classification is absolutel}' necessar\- if we wish to acquire a clear 

 knowledge of the Animal Kingdom as a whole. The simplest system 

 of classification is that named morphological (from the Greek words niorphc 

 form, and logos science), by which animals that are constructed on the 

 same plan are placed in the same group. The first grand division we 

 make is between animals that have a backbone, the Vertebrata, and 

 animals that have no backbone, the Invertebrata. 



The Invertebrat.\ are divided into five sub-kingdoms: PROTOZOA, 

 structureless jelly-like creatures of minute size ; Ccelenterata, animals 

 without a heart or nervous S3-stem, such as the ordinary " Sea Nettle "; 

 AxNULOlDA, a class which contains the " Star-fishes " and " Tape-worms "; 

 Annulosa, animals composed of different segments arranged one behind 

 the other ; to this sub-kingdom belong forms so widely different to the 

 eyes of the superficial observer as " Earth-worms," " Lobsters," " Spiders," 

 "Bees" and -'Butterflies." Lastly, the MoLLUSCA; of which the best 

 known arc the " Oyster" and the " Snail." 



The Vertebrata are so-called from the Latin word vertebra (joint 

 of the backbone), and possess a backbone made of many parts joined 

 together. Each joint consists of a central portion which helps to give 

 rigidity to the body and support to the limbs. On the upper part of this 

 central portion are certain projections, called in technical language 

 processes, that form a protection to the spinal cord ; on the lower part 

 are similar processes which cover the great descending artery. The 

 joints of this backbone from the top of the neck to the end of the tail 

 are made up of similar parts. In the neck we do not find ribs, but 

 the rudiments of ribs. In the back the lower bon)- processes are elon- 

 gated into ribs ; in the loins the processes again degenerate ; in the 

 haunches they become confluent with bones that form a cylindrical 

 covering for the softer vessels, and offer a strong fulcrum for the lower 

 limbs. Nay more, the skull is made up of parts corresponding to four 

 vertebra. 



The nervous system of the Vertebrates consist of the brain, enclosed 

 in the bony cavity of the skull, and the spinal eord, whence spring at inter- 

 vals symmetrical pairs of nerves distributed to the voluntary muscles. 

 The organs of sense become more perfect, the e3'es are invariably two in 

 number, and sagacity is developed in proportion as the nervous centres 

 expand. The blood is red, and the temperature of the bodv higher than 

 that of the surrounding medium. But this temperature differs so much 



