EESEAECHES ON THE OOGENESIS OF THE TORTOISE, 

 CLEMMY8 MA RMORA TA . 



BY 



JOHN P. MUNSON. 

 With 7 Plates. 



TABLE OF CONTENTS. 



PAGE. 



Introduction 311 



Description of the Tortoise 312 



Methods 313 



The Ovary 313 



The Germinal Mass 314 



The Oogonia 314 



The Centrosome 315 



Division of Oosonia 316 



Formation of Follicle 316 



Differentiation of the Oocyte 317 



The Egg 319 



Stages of Growth 319 



Stage I 320 



Germinal Vesicle 320 



The Nucleoli 320 



The Cytoplasm 320 



The Centrosome 321 



Cytoplasmic Areas 321 



Stage II 323 



The Nucleolus 322 



The Germinal Vesicle 322 



Position of the Germinal Vesicle 323 



PAGE. 



Excentricity of the Germinal Vesicle. 323 

 The Cytocenter 324 



Staining Effects 324 



Stage III 325 



The Germinal Vesicle 335 



Distance of Germinal Vesicle from the 



Cytocenter 326 



The Cytocenter 326 



The Yolk-Nucleus 327 



Plasma Channel 328 



The Yolk 329 



The Egg Membrane 331 



On the Organization of the Egg 331 



The Cytoreticulum 333 



The Centrosome .3.33 



Chemical Processes *34 



The Growth of the Egg 338 



Polarity of the Egg 338 



The Egg Axis 337 



Literature 337 



Reference Letters 340 



Explanation of Plates 341 



Cytological problems are so numerous and yet so prominent in the 

 minds of investigators that it may seem unnecessary to call attention to 

 them again here. Oscar Hertwig, E. B. Wilson, Whitman and others 

 have stated these problems so well that I cannot do better than to refer 

 to these writers, and call attention to the following suggestive quotation 

 from Wilson, 84 : " On the one hand, it has been suggested by Flem- 

 ming and Van Beneden, and urged especially by Whitman, that the 

 cytoplasm of the ovum possesses a definite primordial organization, which 

 exists from the beginning of its existence even though invisible, and is 

 revealed to observation through polar differentiation, bilateral symmetry, 

 and other obvious characters in the unsegmented egg. On the other 

 hand, it has been maintained by Pfliiger, Mark, Oscar Hertwig, Driesch, 



American Journal of Anatomy. — Vol. III. 



