[AxNAXS N. Y. AcAU. Sci., Vol. XXIV. pp. 319-346, Pll. XXII-XLI. 



31 March, 1915] 



DEVELOPMENT OF THE NEUEAXIS IX THE DOMESTIC CAT 

 TO THE STAGE OF TWEXTY-OXE SOMITES ^ 



By H. vox W. Schulte axd Frederick Tilxey 



CONTENTS /V^W 



Introduction 319 



Description of embryos 



Embryos prior to the appearance of intersomitic clefts 321 



Embryos of one somite 321 



Embryos of two somites 321 



Embryo of three somites 322 



Embryo of four somites 322 



Embryos of seven somites 323 



Embryos of eight somites 324 



Embryo of nine somites 324 



Embryos of ten somites 326 



Embryos of twelve and thirteen somites 327 



Embryos of fourteen somites 327 



Embryo of sixteen somites 329 



Embryo of seventeen somites 329 



Embryo of nineteen somites 3.30 



Embryo of twenty-one somites 331 



Ganglionic crest 3.32 



Closure of the Neural Tube 336 



Prosencephalon 338 



Mesencephalon 342 



Rhombencephalon 344 



Page ;3oy^^ 



.3'^1 ^fiK' 



Introduction 



The present paper is a study of the morphogenesis of the neuraxis in 

 its early stages, with especial reference to an attempted interpretation 

 of the forebrain in terms of the longitudinal zones of the neural tube, 

 viz., the basal and alar laminae, and the ganglionic crest. The theoretical 

 problem can be stated briefly. Since the ganglionic elements are in- 

 cluded in the wall of the neural tube at the time of its separation from 

 the ectoderm — Xeumayer has shown this for reptiles, and it is also true 



1 Presented in abstract hy the senior author at the meeting of 11 May, 1914, under 

 the title "Early Stages in the Development of the Brain in the Domestic Cat." 

 Manuscript received by the Editor, 17 September, 1914. 



(319) 



