234 ANIMAL PHYSIOLOGY. [LESSON 70, 



ring, beset wiih ganglia, is not found, except in rare cases ; it is a 

 nervous commissure (or band) connecting the cephalic ganglia, and 

 passing, not around, but behind the oesophagus. Then the pedal 

 ganglia (in those molluscs possessing a foot) and the branchial ganglia 

 are variously disposed now in one place, now in another hence 

 Owen, with far greater propriety, called Cuvier's Mollusca, Hetero- 

 gangliata (eteros, other ; genos, kind). 



1055. The designation of the next sub-kingdom, by Owen, as 

 compared with Grant, is of less consequence ; and whether we ex- 

 press the " double nervous chord " with Grant, or speak of the sym- 

 metrical arrangement of the ganglia in this class, with Owen, who 

 calls them, from the latter circumstance, Homogangliata (omes, the 

 same; genos, kind), matters not, either expression being equally correct. 



1056. We come to the last division of the animal kingdom, Ea- 

 diata of Cuvier, Cyclo-neura of Grant. 



1057. Owen is content to take the statement of Tiedemann in re- 

 lation to the Star-fishes ; moreover, he has a preparation of Asterias 

 papposa, in the college Museum, prepared by the hand of the immor- 

 tal Hunter, but whether the author designed it to represent the ner- 

 vous system (which it certainly does not), or a portion of the vascu- 

 lar system (which it assuredly does), is left to conjecture. 



1058. For those animals of the Radiate division in which Owen 

 believes a nervous system has been recognized, he proposes the word 

 Nematoneura (nema, a thread; neuron, a nerve). But in common 

 with many others, he is by no means satisfied that a nervous system 

 has been discovered in some of the class of Cuvier's Radiata ; and for 

 these he proposes a very significant designation Acrita, confused. 



1059. The lower animals exhibit all the manifestations of a ner- 

 vous system, whether it can be detected or not. 



1060. It is presumed, therefore, to exist, but under such circum- 

 stances that even the microscope fails to detect it as an independent 

 organism it is diffused or confused, and hence the expression is a 

 good one. 



LESSON LXX. 



NEBVOUS SYSTEM, CONTINUED. 



1061. The classification of the three first classes of the animal 

 kingdom, especially by the last authority, is undeniably good ; much 

 doubt exists, however, as to whether a nervous system really exists 

 in any individual of the last (Radiata) or not. 



