PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. [1885. 



EXPLANATION OF PLATE VH. 



Eefekenceb: — a, anal fin J ah, air-bladder; al, urinary vesicle ; au, auditory vesicle ; &a, bulbosaortsB; 

 c, pericardiac cavity; cs, coraco-scapolar cartilage;/, pecten; i, intestine ; i, Uver : m, 

 muscular somites ; mh, mid-brain ; Mk, Meckel's cartilage ; n, nasal pit ; o, generative 

 gland ; pn, mesonepbros : pq, palato-quadrate cartilage ; pp, peritoneal cavity ; r, muscles 

 of the eye : sc, cavity between the viscera and yelk ; sv, sinus venosus ; v, vent or anus ; 

 vv, vitelline vessels ; ve, ventricle : TTd, Wolffian or segmental duct ; y, yelk ; yh, yelk 

 hypoblast or periblast. 



Pig. 4. — Foetus hardened, in its follicle to show the way in which it is coiled up. x 15. 



Fig. 5. — Transverse section of an advanced embryo through the yelk-sac and body in the vicinity of 

 the pectoral fins, x 29. 



Fig. 6.— Longitudinal vertical section of an advanced embryo somewhat off of the median line, x 29, 



Fig, 7. — Longitudinal vertical section of a similar embryo nearer the median line than the preceding, 

 X 29. 



