THE DEVELOPMENT OF THE HYPOPHYSIS IN 
SQUALUS ACANTHIAS 
EK. A. BAUMGARTNER 
Institute of Anatomy, University of Minnesota and Washington University Medical 
School! 
FORTY-THREE FIGURES 
CONTENTS 
LEDER CLION Tle Pere Sher c ee ER  Gocnc Oh CPC Oe ene 2A el hehe eee 2 391 
LLG SIPTN ID: 6 ona oad ees ticle oe le eae a ee Il a ee 392 
PEPE Tay Ol Omae we ie Se TTR Sch Sa seater nik 0.6, bve, ae 5 oor AAA a Ed Se i ES 392 
ere 8) OP PUL REL SGU Vice ca <a oa v bjoGpeie aca © mds = dace fal eR ws ensues 396 
Morphology and morphogenesis......................0. PE SHO TOE 23 Sua Nee eats 400 
1. Description of the hypophysis in the pup stage.....................6. 400 
2. Banly development of the hypophysis. ........0. 6. (eR E ee 407 
=. later development ‘of. the hypophysis. ...........:.. dads neues os be ema 412 
4. The hypophysis of the adult.............., a 6 a hws: 2 a eae ae eal 417 
Histology and Histogenesis: .. 00)... 00.0 c ee oye Sie: = a6 ae aa ae Re 425 
PeMaisvolery or the adult by popltysisc. as... <0. . 20s sot cae te rene es 425 
Peristaeetesia Ol bey POP YSIS. 3.) Jgus's<:.) x: «0s as seeped daleuieidele cieden 431 
3. Development of the interhypophyseal canal.................-..-2.008- 438 
4-, Developnient, of the hypophyseal stalk. ..:.... .. 2.0 duinesee «dee sos dans 440 
PSULINIINTCLINV RRR soerctvet Ser sheet eens ea icv Tears Se Soo'a, Se veietd $ alata eee acres 442 
PiSREN LICH BORE ER EDN At hos at eer Fats 21s ie VSN A ie ib Las ailb jac, wane a DK Li ee ee ee aS 445 
INTRODUCTION 
Although considerable work has been done on the hypophysis 
of elasmobranchs, many points still remain concerning which 
there has been much discussion and which evidently require 
further investigation. It was thought that an intensive study 
of the history of this organ in one form might be of value. 
The embryos used are from the collection of Dr. R. HE. Scam- 
mon and from the large series which form a part of the embryo- 
1 This work was begun while at the University of Minnesota and completed at 
Washington University Medical School. 
391 
JOURNAL OF MORPHOLOGY, VOL. 26, NO. 3 
SEPTEMBER, 1915 
