544 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



PLATK XI, I. 

 (Stage VI.) 



FIGS. 11 1-1 1<S. Transverse serial sections of egg-nauplius in stage shown in Fiji. !(>!>. Plane ol 

 section indicated iu Fig. Ill, which is from au embryo a trifle less advanced. The 

 lobular condition of the enlarged optic disks is well shown in Figs. 114, 115. In 

 Fig. 1 14 a delaminating cell (<'<:) at the surface <>f the optic lobe is cut, and in Fig. 

 115 a superficial ectodermic cell next the brain is dividing perpendicularly. The 

 intimate fusion of the braiu and the optic ganglion is seen iu Figs. 115, 116. Fig. 

 1 17 cuts the stomodit'iiiii passing through the mouth and the antenna 1 ,. Mesoblast is 

 already well established in the. pockets of all the appendages, as indicated at au 

 earlier period. Degenerating cell products (<S'., A. Y. <S'., Fig. 18) are very abundant 

 in the region of the stomocbeuiii, and occur also in the appendages (N.-S. 1 , S'. C., Fig. 

 118). x -'!!. 



REFERENCE LETTERS. 



I. I / ), . I UK [I II. I I l>Ull. 



A. (11), autennular buil. 

 I. )". /?., alteration products of yolk. 



''/. X., cells partially covering brain, derivatives from yolk-wandering cells. 

 KC. , surface cell of ectoderm dividing horizontally. 

 Kct., Kp., ectoderm, 

 t/rf., mamlibnlar bud. 

 Mil. <i., maudibular gaugliou. 

 M. F., median furrow. 

 ". G., optic ganglion. 

 <>. L., optic lobe. 

 AY/., protoplasmic reticulum. 

 .>'. N. 1 , products of cell degeueration. 

 N. i>. G., brain. 

 xt<l., stomoda'um. 

 for., vaciiole. 

 T., F. C., yolk. 



