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PROCEEDINGS OF THE AMERICAN ACADEMY. 



ferent fluids no evidence of hooks on the penis appeared. Inasmuch 

 as Bergh cites as his only authority Verrill, it is apparent that his 

 statement " penis armata " is a mere supposition based on the fact that 

 it is armed in Polycera. Therefore, this characterization of the genus 

 Polycerella will have to be changed to " penis unarmed." 



The vas deferens is a narrow duct of uniform diameter throughout 

 its entire length opening into the prostate duct ; it passes by several 

 turns to the base of the penis, the latter part of its course depending 

 upon the position of the penis in the body. The vas deferens is heavily 

 ciliated throughout its whole length. 



■pd.p. 



FiGUHE 9. Drawing (diagrammatic) of nervous system seen from the right 

 side, gn.buc, buccal ganglion; gn.cb., cerebral ganglion; gn.olf., olfactory- 

 ganglion; gn.opt., optic ganglion; gn.pd., pedal ganglion; gn.vsc, visceral gan- 

 glion; n., nerve to integument; n.olf., olfactory nerve; n.pd.a., anterior pedal 

 nerve; n.pd.p.; posterior pedal nerve; oc, eye; ot'cys., otocyst. 



9. The Nervous Si/stem. 



The nervous system is simpler in some respects than it is in the 

 larger Eolidae and in some of the Doridae, although showkig the same 

 concentration of the ganglia into a nerve collar around the esophagus 

 immediately behind the pharynx. There are three pairs of large gan- 

 glia, — cerebral, pedal, and visceral, — the usual small pair of buccal 

 ganglia, and several minor ganglia to be described afterwards. 



The cerebral ganglia (Figures 9, 10, gn. cb.) are nearly spherical, the 

 antero-posterior diameter being slightly shorter than the others. They 

 are the largest of the ganglia, each being about 30 by 20 by 20 micra, 

 and cover the dorsal surface and a small part of each side of the esoph- 

 agus. The cerebral commissure (Figure 10, co'ins. cb.) is three micra 

 long and six micra wide. The cerebro-pedal connective (Figure 9) 



