144 Wisconsin Academy of Sciences, Arts , and Letters. 
EXPLANATION OF PLATE XIII. 
Fig. 21. 
Fig. 22. 
Fig. 23. 
Fig. 24. 
Fig. 25. 
Fig. 26. 
Fig. 27. 
Fig. 28. 
Sagittal section of brain through, the center. D. 3. 
opt. g., optic ganglion, supr. g., supra-oesopha- 
geal ganglion, oes., oesophagus'. 
Section through brain, but a little to one side of the 
preceding. D. 3. 
Section of brain cut in line drawn from; a to> b in fig. 
21. D. 3. s. g., supr a-o esophageal ganglion, 
ant. gl., antennulary ganglion, o. c., circum- 
oesophageal commissures, oes., oesophagus, ant. 
g2., antennary ganglion, inf. g., infra-oesopha- 
geal ganglion. 
Dorsal view of ventral cord, ganglion cells only show¬ 
ing. B. 3. 
Transverse section of second ganglion. B., dorsal. 
D. 3. 
Transverse section just a little anterior to the preced¬ 
ing. 
Ventral nerve cord, lateral view. B. 3. 
Section of eye. D. 3. rt, retinal cells, tp., tapetum. 
pg., pigment. 
Fig. 29. Section of eye from above. D. 3. ant., anterior. 
pg., pigment cells, nu., nuclei of retinal cells. 
Fig. 30 Ovary, d., dorsal, a., anterior. The figures repre* 
sent the four different zones. 
