542 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



PLATE XL. 

 (Stage VI.) 



FIG. lO'.l, Sketch of egg-nauplius. Anus not so clearly .seen 111 surface view, as represented in 

 this anil the following figure. Mouth on a level with auteunules. x 72. 



FIG. 110. Sketch of older embryo. Appendages all bending backwards and inwards toward 

 middle line, x 72. 



FlG. 111. Egg-nauplius less developed than shown in Fig. 109, but from same batch of eggs. 

 The position of the mouth, which is post-antennal from the first, is now on the middle 

 line between the antenna* and the antennules. The probable position of the anus 

 is indicated, but it could not be clearly seen. The bud which represents the endop- 

 odite of the antenna, is just appearing on the right side, x 157. 



FIG. 112. Oblique transverse section, through egg-nauplius of a common shore crab of Beaufort, 

 North Carolina, probably Srxiiniiii. x2M(i. 



FIG. 113. Median longitudinal section, through a similar embryo. The egg membranes are not 

 naturally shown. The yolk is diagramatically represented. Wandering cells occur 

 in it ( 1". C.), and in Fig. 113 degenerative products (Dey.) are met with. x28G. 



REFERENCE LETTEliS. 



A., anus. 



A. (I), anteuual bud. 



A. (I), antenuular bud. 



.1ft., thoracico-al>domiual fold. 



' '!>., eggshell. 



Deg., degenerative cell products. 



Iff., ectoderm. 



Gl., ectoblast of neural plate. 



H., inesoblast cells, forming rudimentary heart. 



Bg., hind gut. 



Lb., labrum. 



J/(J., tiiaridilmlar bud. 



Men., incKoblast below surface. 



<). <!., optic. ganglion. 



". /,., optic liilir. 



'*. .s'. t:.,,S. <>. (,'., riidiinuiitiiry brain. 

 .*>'/<(., stoniodit'Uiii. 



I'oc., vacuole. 



)". C., wandering cells. 



Xuuibers 114-125 mark tue jilaUL'B of the tiausverse and lougitudiiial si'ctions rc]ircseiitcd mi I'ls. 

 XLI-XLIII. 



