338 



WILLIAM PATTEN. 



nerve of the body, resembling rather one of the lateral cords 

 of the central nervous system ; or it may be compared with 

 the " Ganglien Zellenstrang'' of Vejdovsky. 



Fig. 7- — -d. Diagram of fore-brain of Limulus embryo, constructed 

 merely to show probable condition from which the parts in the older 

 embryos are derived, and the relation of these parts to similar ones in 

 fore-brain of Scorpion. B. Diagrammatic view of fore-brain at later 

 stage, showing the union of ganglionic pits and eye-tubes. 1-4. Dia- 

 grammatic sections, showing origin of eye and unfolding of brain and optic 

 ganglion. 5. Section through the third eye-plate and ganglionic inva- 

 gination. B, 5 indicates direction of section. /'-^. Lobes of fore-brain. 

 br. Braiu. e'-^ Eyes of the three brain-segments, g. »'-^. Ganglionic 

 pits. m. b. Mid-brain, or fourth neuromere. m. e. Median eye of first 

 segment, m. e'. Median eye of second segment, n. I. e. Nerve to lateral 

 eye. np. Neuropore. ce. g. Ganglion to stomodeal nerves, op. y'-'. 

 Optic ganglia, op. g.^ Optic ganglion to lateral eye and to e^. 



The segmental thoracic sense-organs and the lateral furrow 

 of Limulus, as shown by their position and mutual relations, 

 are, respectively, serially homologous with the cephalic sense- 



