534 MKJMoiKa oi' 'HUE katiunal academy of sciences. 



PJ.ATK XXXVI. 



(Stage V.) 



Figs. 86, 87. Parts of longitudinal sectioi).s of embryo seven or eight hours older than that shown 

 iu Fig. 72. The optic disk (0. D.) is cut in Fig. 86, and in Fig. 87 its inner part is 

 involvlid, with the outer border of the thoracic abdominal phite. There is no sharp 

 demarcation between the protoplasm and the yolk, as is indicated by the dotted lines 

 under the embryonic layers, x 291. 



Figs. 88-89. Longitudinal serial sections through the entire embryo, somewhat younger than the 

 last, and six hours older than that represented in Fig. 72. The optic disk is sectioned 

 in Pig. 90 through its central proliferating area (C. J/.), and the rudiments of the 

 three naupliar appendages appear in Fig. 89. xll5. 



Fhj. 91. Transverse section cutting optic disks of embryo about nineteen hours older than that of 

 Fig. 72 and twelve hours older than that represented by Figs. 80, 87. Wandering 

 cells (Y. C) have traveled to remote parts of the surface, and karyokiuetic figures 

 (Y. C,^, Fig. 89) i)rove that they are in active division. xll5. 



REFERENCE LETTERS. 



A. (/), rudiment of first .antenna. 



A. (II), rudiment of second imtenna. 



Ab. P., ventral plate. * 



App., area of appendages. 



Ch., eggshell. 



C. M., proliferating area of optic disk. 



fc, migrating ectoblast cell. 



Ep., ectoderm. 



Md., rudiment of mandible. 



0. D., optic disk. 



S., product of degenerating chromatin. 



St. J., sternal area. 



T. Cd., trausverse cord. 



1". C, F. C.'-^ wandering cells. 



Y. S., yolk sphere. 



