author's abstract of this paper issued 

 by the bibliographic service juxe '15. 



STRUCTURE AND DEVELOPMENT OF THE SENSE 



ORGANS OF THE LATERAL CANAL SYSTE^I OF 



SELACHIANS (MUSTELUS CANIS AND 



SQUALUS ACANTHLIS)' 



SYDNEY EVANS JOHNSON 



Insti'ucto)' in Anatomy, Northirpfttern. Utiiversih/ Medical School 



EIGHTY-THREE FIGURES 



CONTENTS 



I. Introduction 1 



II. Brief comments on the literature 3 



III. Material, methods and terminology 9 



IV. Observations 19 



A. Mustelus canis 19 



1. Distribution of the canals and their gross innervation 19 



2. Structure of the sensory canals 22 



a. General anatomy 22 



b. Histology of the sensory epithelium 23 



c. Peripheral terminations of the nervus lateralis 26 



3. Development of the sensory canals of ]\Iustelus 32 



B. Squalus acanthias 34 



1. Development of the sensory canal system 34 



a. Early stages of development — 9 to 36 mm 34 



b. Later stages of development — 40 to 72 mm 58 



2. Structure of the sensory canals of the adult 65 



V. Summary, conclusions and comparison of the forms studied 69 



VI. Bibliography 73 



I. INTRODUCTION 



For nearly 200 years after its discovery in selachians, in 1664, 

 the canal system of fishes was supposed to l^e mucous secreting, 

 and it was not until 1850 that Leydig produced histological 

 evidence showing that the organs within the canal system of the 

 head of bony fishes are sensory in nature. 



1 Contribution from the Zoological Laborator}- of Northwestern Universit}' 

 under the direction of William A. Locy. 



1 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 28, NO. 1 

 AUGUST, 1917 



