546 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XLII. 



(Stage VI.) 



Figs. 119-122. Serial transverse sections of the egg-nauplius, continued from PI. xli. In Fig, 

 120 a transverse row of cells with large clear nuclei is seen. This is probably a 

 series of budding ectoblasts and mesoblasts, already referred to. Wandering cells 

 appear to be settling down upon all parts of the embryo. In the thoracico-abdomi- 

 nal fold (Fig. 122, tom.) the abdominal muscles are already nndergoing differentiation 

 out of the mesoblast of the ventral plate. x295. 



REFERENCE LETTERS. 



A., ;in.al invaginalion. 

 J. {II), antennal bud. 

 Ab., alKlomeu. 



A. T. S., yolk umlergoing change. 

 B.Z., budding zone. 

 \ lict., ectoderm. 



/TV/., intestine. 

 Aid., ni.andible. 

 Mil. (1., mandibular ganglion. 

 Mcs., nii'sodcrui. 

 M. F., median gmovn. 

 Mu., muscle cells. 

 Mx. (1), first maxillary bud. 

 8.', products of cell degeneration. 

 <S. C, degenerating cells. 

 Y., yolk. 



T. C, T. C, wandering cells. 

 Vae., vacuole. 



