ON THE DEVELOPMENT OF THE DIGITIFORM 

 GLAND AND THE POST-VALVULAR SEGMENT OF 

 THE INTESTINE IN SQUALUS ACANTHIAS 



E. R. HOSKINS 



From the Institute of Anatomy, University of Minnesota, and the Osborn Zoological 

 Laboratory of Yale University 



THIRTY FIGURES 



CONTENTS 



1. The digitiform gland 329 



Introduction 329 



Development 333 



Structure in adult 345 



Summary 350 



2. The post-valvular segment of the intestine 352 



Introduction 352 



Development of external form 352 



Occlusion 354 



Summary 358 



3. Bibliography 359 



THE DIGITIFORM GLAND 



Introduction 



The results here presented were nearly completed in 1914 

 but laid aside temporarily for another research. An abstract 

 of the first part of this paper has already been published (Hos- 

 kins '15). The work was made possible through access to a very 

 complete serial collection of Acanthias embryos obtained in 

 part from the Harpswell Laboratory, and belonging to Dr. 

 R. E. Scammon, and to others secured from the Harvard Em- 

 bryological Collection through the kindness of the late Dr. C. S. 

 Minot. I desire here to thank Dr. Scammon for suggesting 

 this investigation, for the loan of material, and for many help- 

 ful criticisms. 



329 



JOURNAL OF MORPHOLOGY, VOL. 28, NO. 2 

 MARCH, 1917 



