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

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



Campodea. The cephalic end is to the right and the train is above. 



X 150. 

 Figs. 25 and 26. Cross sei .rough the brain and first ventral ganglion of 



Campodea taken at different levels. X 150. 

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



the dorsal side is above, the cephalic end at the left. X 150. 

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



the dorsal side is up. X 150. 

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



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. 



