THE ORIGIN OF THE LATERAL LINE PRIMORDIA IN 

 LEPIDOSTEUS OSSEUS^ 



F. L. LANDACRE AND A. C. CONGER 



THIRTY-FOTJR FIGURES 



CONTENTS 



Introduction 576 



Historical review 577 



Material and method 582 



The 10-mm. embryo (general) 583 



Early stages 584 



The preauditory region 587 



a. The preauditory placode ,..'-. 588 



b. The ectodermal gill thickening ■••■•,• 590 



c. The epibranchial placode 591 



d. The posterior extension of the epibranchial placode 592 



e. The primordia of supra-orbital and infra-orbital sensory lines 593 



f . The primordium of the hyo-mandibular line 596 



The postauditory region 597 



Stage XIII 598 



Stage XIV 600 



Stage XV 600 



Stage XVI 601 



Stage XVII 602 



Stage XVIII 603 



Stage XIX 603 



Stage XXI 604 



Summary and discussion 608 



The preauditory region 608 



The postauditory region 611 



Literature cited 616 



1 Contributions from The Department of Zoology of the Ohio State Univer- 

 sity, No. 37. 



575 



THE JOURNAL OP COMPARATIVE NEUROLOaT, VOL. 23, NO. 6 



