NERVOUS SYSTEM. 



81 



At a higher stage of development a circum-pharyngeal nerve ring 

 is developed. With the commencing segmentation of the body the 

 number of ganglia increases, and in addition to the brain there is 

 present a ventral nervous system consisting either of ventral cord 



D 



FIG. 76. Alimentary canal and 

 nsrvous system of Mesosto- 

 mum Ehrenbergi (after Graff). 

 G, the paired cerebral ganglia 

 with two eye-spots ; St. one 

 of the two main lateral nerves ; 

 Z>,alirnentary canalwithmonth 

 and pharynx. 



C rt 



G 3 - G 



FIG. 77. Nervous system of FIG. 78. Nervous system 



the larva of Coccinella 

 (after Ed. Brandt). G, su- 

 pra-oesophageal ganglion 

 or brain ; Gfr, frontal 

 ganglion; Sy, subosso- 

 phageal ganglion ; G',-G", 

 the eleven ganglia of the 

 ventral chain of thorax 

 and abdomen. 



of adult Coccinella (after 

 Ed. Brandt). A(j, optic 

 gansrlion. The other let- 

 ters as in fig. 77. 



(Gephyrea) or of a ventral chain of ganglia, which may have a 

 homonomous (Annelids) or heteronomous (Arthropods) arrangement 

 (figs. 77 and 78). The concentration of the nervous system begun 



6 



