544 MEMOIKS OF THE NATIONAL AOADEMY OF SCIENCES. 



Plaik XLl. 



(SUij,'e VI.) 



Figs. 114-llS. Transverse serial sections of egg-miui)lius in staye shown in Ji'ij^. 109. Plane of 

 sei^tion indicated in Fij?- HI, which is from an embryo a trifle less advanced. The 

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

 Fig. 114 a deUiminating cell («■.) at the surface of the optic lobe is cut, and in Fig. 

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

 intimate fusion of the brain and the oi)tic ganglion is seen in Figs. 11.5, 116. Fig. 

 117 cuts the stomodieum passing through the mouth and the antenna;. Mesoblast is 

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

 earlier period. DegenL'rating cell products (>S., A. Y. S., Fig. IS) are very abundant 

 in the region of the ^tomodieum, and occur also in the appendages (>S.~S.\ 6'. C, Fig. 

 118). x2!)l. 



REFERENCE LETTERS. 



A. (/), antenual Inul. 



A. (II), antennular bud. 



A. Y. S., alteration products of yolk. 



Ct. S., cells partially covering brain, derivativos from yolk-wanderm;; bcIIs. 



ec, surface cell of ectoderm dividing horizontally. 



Ect., Ep., ectoderm. 



3/(i., mandibular bud. 



Md. (r., mandibular ganglion. 



J/. -F., median furrow. 



O. G., optic ganglion. 



O. L., optic lobe. 



Ret., protoplasmic reticulum. 



.S. A'.i, products of cell degeneration. 



5. O. G., brain. 



Sid., stomodaium. 



¥ac , vacuole. 



F., r. C.,-yolk. 



