542 MEMOIRS OF THE NATIONAL ACADEMY OP^ SCIENCES. 



Platk XL. 

 (Stage VI.) 



Fig. 100. Sketch of egg-naupliuss. Auus uot .so clearly seen in surface view, as represented in 

 this and the following figure. Mouth on a level with antennules. x 72. 



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

 middle line." xTii. 



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

 The position of the mouth, which is postantennal from the first, is now on the middle 

 line between the antenniB and the ajitennnles. 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-nanplius of a common shore crab of Beaufort, 

 North Carolina, jirobably Sesarma. x286. 



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 {Deg.) are met with. x286. 



REFERENCE LETTERS. 



A., anus. 



A. (I), auteuiial bud. 

 A. (I), antennnlar bvid. 

 AJ>., thoracico-abdoraiaal fobl. 

 Cli., eggshell. 



Dei/., degenerative cell jtroducts. 

 Ep., ectoderm. 



GL, ectoblast ofnenral plate. 

 H., mesobla.st cells, foriuiug rudimentary heart. 

 Bg., hind gut. 

 Lh., labruxu. 

 Md., mandibular bud. 

 jUes., mesoblast below Kurfacc. 

 O. 0., optic ganglion. 

 O, Lr., optic lobe. 



O. S. (i.-i S. O. G., rudiinentary brain. 

 .S«rf., Btoinodasuni. 

 Vac, vacuole. 

 F. C, wandering cells. 

 -yumbem 114-125 mark the plants of the. transverse and longitudinal sections represented on J'ls. 



XLI-XLIII. 



