Fig. 22. Cross section through the first thoracic ganghon of Evalljapax. X 50. 

 Figs. 23 and 24. Longitudinal sections through the brain and ventral ganglion of 

 Hk^^m Cainpodea. The cephalic end is to the right and the brain is above. 



P X 150. 



Figs. 25 and 26. Cross sections through the brain and first ventral ganglion of 

 Pl^ Campodea taken at different levels. X 150. 



Fig. 27. Longitudinal section through the first thoracic ganglion of Campodea, 

 pPp •M^l the dorsal side is above, the cephalic end at the left. X 150. 

 Fig. 28. Longitudinal section through the second thoracic ganglion of Campodea, 

 ■l^ the dorsal side is up. X 150. 



Fig. 29. Longitudinal section through the brain of Machilis. Only one-half is 

 |*|ig shown. The optic lobe region is at the top of the figure. X 150. 



Fig. 30. Longitudinal section through the brain and two ventral ganglia of 

 Machilis. X 150. 



