326 
BULLE'J'IN OF THE UNITED STATES FISH COMMISSION. 
EXPLANATION OF PLATE LIX. 
Fig. 53 Abdominal viscera of young sturgeon, viewed from below, showing a bristle, M"", passing 
through opening in mesentery of second loop of intestine, and with the under wall of 
pancreas, P, removed to show its glandular cavities, which are much less numerous in the 
young Sturgeon than in the adult. Natural size. 
Fig. 54. Viscera of young sturgeon, viewed from above; swim-bladder, W, intact. Natural size. 
Fig. 55. Viscera of young sturgeon, viewed from above, with spiral valve laid open to show its seven 
turns and with the swim-bladder VN cut open aud laid to one side to show the wide pneu- 
matic duct PN joining the alimentary canal just at the beginning of the first or gastric 
loop of the latter. The spleen S aud S' is also exposed. Natural size. 
Fig. 56. Viscera of young sturgeon, viewed from above, with upper wall of swim-bladder cut away to 
show the cleft-like opening of the pneumatic duct into its anterior end, with the muscular 
fibers radiating from it into the door of the pneumatocyst or swim-bladder. Natural size. 
