108 



FUNCTIONS OF THE NERVOUS SYSTEM. 



Fig. 11. 



Nervous System of Larva of SPHINX LIGUS- 

 TRI, after Newport; A, cephalic ganglia; 1-11, 

 ganglia of the trunk, disposed at nearly equal 

 distances; the last is formed by the consolida- 

 tion of the llth and !S2th. 



141 . The animals composing the group 

 ARTICULATA, all present, in a more or less 

 evident degree, a division into segments, 

 which have an obvious tendency to re- 

 semble one another, as in the Radiata. 

 In those in which these segments differ 

 but little (as in the Centipede, or the Ca- 

 terpillar of the Insect), the nervous system 

 is a repetition of similar parts ; disposed, 

 not in a circle, as in the Radiata, but in a 

 continuous line. The most interior of the 

 ganglia, however, has an evident pre- 

 dominating influence over the rest, for 

 the reason just specified; and this influ- 

 ence will be found, by comparison in other 

 classes, to diminish with the loss, and to 

 increase with the development, of the 

 faculties of special sensation, which have 

 their seat there. The locomotive powers 

 are just as predominant in the Articulated 

 series, as are the nutritive functions among 

 the Mollusca. Accordingly, we find the 

 development of the Nervous System to 

 bear a special reference to them ; and the 

 sen sori -motor divisions of it can be more 

 distinctly separated than in the Mollusca, 

 from the portion which ministers to the 

 organic functions. 



142. The general arrangement of the 

 Nervous System differs so little, except as 

 to the degree of concentration of the gan- 

 glia, in the different classes of this sub- 

 kingdom, that it is of little consequence 

 what example we select. It will be con- 

 venient to take for illustration that of the 

 Larva of the Sphinx Ligustri, or Privet 

 Hawk-Moth, which has been minutely 

 described by Mr. Newport. Here we ob- 

 serve a chain of ganglia running from one 

 extremity of the body to the other, along 

 the ventral surface, and in the median 

 line. These ganglia are connected by 

 trunks, which, on close examination, are 

 seen to consist of two cords closely united. 

 The cephalic ganglion is bilobed; evi- 

 dently consisting of two masses, which 

 are united on the median line. These re- 

 ceive the nerves of the eyes and antennae ; 

 but they are still of small size, in accord- 

 ance with the low development of the sen- 

 sory organs. The ganglia of the longi- 

 tudinal cord are nearly equal, from one 

 extremity of the body to the other. Each 

 sends off nerves to its respective segments ; 

 and the branches proceeding from the 



