LESSON 69.] NERVOUS SYSTEM. 233 



(unus, one) shells, and the many forms of naked similar creatures 

 found in the ocean. 



1044. The ARTICULATA have their bodies composed of a variable 

 number of distinct rings, or segments, jointed to each other, such as 

 Lobsters, Insects, Centipedes, Worms, &c. 



1045. The RADIATA are so called from the several members of 

 the body radiating from the central portion, as in the Star-fishes. 



1046. Dr. E. E. Grant, of Edinburgh, offered, some thirty years 

 ago, a classification of the animal kingdom which should be based 

 upon the development of the nervous system alone. Hence the new 

 classification, as compared with Cuvier's, stood thus : 



1047. Cuvier. Grant. 

 VERTEBRATA, SPINI-CEREBRATA. 

 MOLLUSC A, CYCLO-GANGLIATA. 

 ARTICULATA, DIPLO-NEURA. 

 EADIATA, CYCLO-NEURA. 



1048. The Oerebro-spinal (brain, spine) axis of man, and all 

 Vertebrates, originated the expression by which Grant designates 

 this sub-kingdom. 



1049. The Mollusca were assumed by this author to possess a 

 nervous chord which surrounded the oesophagus, and upon which 

 ganglia were placed ; hence Cyclo-gangliata (circle ; ganglions.) 

 The nervous system of Cuvier's Articulata is found to consist, pri- 

 marily, of a double nervous chord, hence Diplo-neura (two ; nerves), 

 but on which ganglia are more or less found. 



1050. The last sub-kingdom, the Radiata of Cuvier, presents (in 

 the Star-fishes, according to Tiedemann) a nervous ring surrounding 

 the oral aperture, but without any ganglion, therefore Cyclo-neura 

 (circular nerve). 



1051. This classification was unquestionably an advance; but 

 another man, younger than Grant, and newer to science, desired to 

 prove the facts upon which the latter system was founded, and this 

 man was Owen. 



1052. With regard to the Vertebrate division but little could be 

 done Cuvier's characters had covered the ground, and the nervous 

 system was found to be arranged on a uniform plan. 



1053. However, in place of the " Spini-cerebrata" of Grant, Owen 

 proposed Myalencephala, as somewhat more expressive, the word 

 being derived from muelos, marrow, and egkephalon, brain. 



1054. When the learned professor examined the Molluscous ani- 

 mals, he found Grant's character to fail ; in this class a nervous 



