8O W. W. SWINGLE. 



EXPLANATION OF FIGURES ON PLATES I-VI. 



All figures were drawn with the aid of a camera lucida. Spencer 2 mm. apo- 

 chromat oil immersion objective and oc. 18 used. Drawings are accurate with 

 reference to the nuclear material and chromatoid body. The cytoplasm, however, 

 is represented in the conventional way. ch, chromatoid body; C, centrosome. 



PLATE I. 



FIG. i. Polar view of metaphase plate in dividing oogonia from ovary of Rana 



catesbiana, twenty-six chromosomes are present. 



FIGS. 2 and 3. Synizesis stages in young oocytes of Rana pipiens larvae. ' 

 FIGS. 4, 5 and 6. Young oocytes of Rana pipiens, showing the pachytene 



threads and the X-chromosome adhering to the nuclear wall. 



