558 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



PLATE XLVI1I. 



(Stage X.) 



FIGS. Ifi2-165. Parts of serial sections through the region of the heart and thoracic-abdominal 

 fold to show the extension and relations of the emloderm. x57. 



FIGS. 166 167. Parts of serial transverse sections of the embryo of Alphens saulcyi. x!25. 



FIG. 168. Median longitudinal section through a slightly older embryo, showing the ventral 

 endodermic ibid (./'), the foregnt still screened from the yolk, and the nervous 

 system separated from the skin. x2l.'7. 



REFERENCE LETTKRS. 



Ab , itlxUmiuii. 



Ali.y. I, first :i Inli mi m. 1 1 ganglion. 



aor., aorta. 



B. I'., Mood .-ell. 



/>'. N. , blood space. 



cc., crystalline cone cells. 



Deg., products of degeneration. 



Ec)>., proximal retinular colls. 



End., eiidodiTiii. 



/., ventral endoderujic fold. 



g.m.a., anterior gastric mimcle. 



H., heart. 



Hg., hindgut. 



imb., intercepting mrmliranr. 



i</., uieHeuteron. 



inn., inuutli. 



nijiyl, first inaxillipudal ganglion. 



Mn. E., extensor muscles. 



Mu.f., flexor muscles. 



O. (!., optic ganglia. 



l>. s., pericardial sinus. 



Ht., retinogen. 



^. O. G., snpra-cesophageal ganglion. 



T., telson. 



Tli., thorax. 



Til. y. I, ganglion of tirst amlinlatory limb. 



y. c., wandering cells. 



