THE EPIBRANCHIAL PLACODES OF LEPIDOSTEUS 
OSSEUS AND THEIR RELATION TO THE 
CEREBRAL GANGLIA 
F. L. LANDACRE 
From the Department of Zoology, Ohio State University 
FIFTY-EIGHT FIGURES 
CONTENTS 
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herstossopharyngeus: camehion, co feeu).8-ieid een eles eee SRE. Set 16 
ULSD OPTIC oT I eae See |, ce) ee NS Oe RL eRe? Bree 17 
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Setrecnienmchiicrie canola OP ON. cote ita) Lets Cee oC oes see 6 eokn e ocn sm OE 18 
Detailed description of the epibranchial placode of VII...................... 19 
Mheclater history, ofuhe epibranchiall placodevofavilly. =. +. ... 425... sso 22 
he origin col thesepioranchtal, placode: of Vales... os 45 ac noe stia ss Sede Se 23 
Summary of the history of the first epibranchial placode.................... 30 
Mhe-epibranchialsplacodetot the LXenerveweene sss eo aon ee eee 32 
Mheshrsixepibranchialaplacodexot: them xterm n er) ries seers inners 36 
Rhersecconcseplbraneimmak placode ofaihnemNerees rit. poeta a eee re oe 38 
The third and fourth epibranchial placodes of the X......................-- 38 
Geuersisummary ind discussions: eeaweee sce. fe chee eee naee o> as 39 
ImiteratwnTereited!..:<:.- ists S.A A ae eee tne chad cre Stat eae es 48 
INTRODUCTION 
A description of the origin and fate of the epibranchial pla- 
codes of Lepidosteus was undertaken with the object of extend- 
ing our knowledge of the part these placodes play in the forma- 
tion of the cerebral ganglia. Ectodermic thickenings, in the 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 22, No. 1 
FEBRUARY, 1912 
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