520 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XXIX. 



Fig. 31. Part of section of egg of Bahaman variety of Alphetis heterochelis, showing two yolk 

 pyramids. Same stage as Fig. 15. Sixty-four cells present, x '-iTi. 



Fig. 32. Part of transverse section of egg-nauplius of A. saulcyi, showing the fold of one of the 

 antennsE and the mesoblastic cells and degenerative products contained within it. 

 x610. 



Fig. 33. Wandering cells in yolk above the same embryo, showing protoplasmic union. xClO. 



Fig. 34. Part of section of egg of the Bahaman heterochelis in egg-nauplius stage, showing wander- 

 ing cells, which have left the yolk and have attached themselves to the superficial 

 ectoblast. The nuclei are flattened against the surface, but are clearly distinguished 

 from the epiblast. x 610. 



Pig. 35. Part of transverse section of older embryo, showing blood cells and wandering mesoblast 

 cell (Jlies.). Eye-pigment beginning to form. xClO. 



Fig. 36. Part of longitudinal section of embryo shown in Fig. 153, to show the degenerative prod- 

 ucts of the dorsal plate, x 610. 



REFERENCE LETTERS. 



App., appendage. 

 A.Y.S., altered yolk. 



B. C, blood corpuscle. 

 Ch., egg membranes. 



C. P., united pseudopodia of two wandering cells. 

 Ect., ectoblast. 



Ep., spindle-shaped nuclei of surface epiblast. 



Met., Mes.', mesoblast. 



Mu., muscle cells. 



Pn., cell protoplasm. 



PL, coagulated blood. 



s, s', degenerative cell products. 



.Sep., inner wall of yolk pyramid. 



S. W., outer wall of yolk pyramid. 



Y. C, wandering cells. 



Y. S., yolk sphere. 



Vac, vacuole. 



