74 
On the Food of Young Fishes. 
Clupeuxe. ' 
We come next to twelve specimens of the gizzard -shad 
(Dorysoma), whose minute fry swarm in countless num- 
bers in the waters of our larger rivers in midsummer. 
These were taken in June and July, from the Illinois F., 
from Ottawa to Peoria. The smallest of the group were 
twenty mm. long by two mm. wide — as slender as cypri- 
noids and nearly cylindrical, although the adult is a high, 
thin fish. I w 7 as greatly interested by the discovery that 
the maxillaries of these smallest specimens are provided 
with teeth — a single row of nine or ten on the lower edge 
— although the mouth of the adult is entirely toothless 
and smooth. The internal structure also differs remark- 
ably from that of the adult, especially in the much great- 
er simplicity of the digestive apparatus. In a young giz- 
zard-shad seven-tenths of an inch long by one-tenth high, 
the intestine was found to pass from the anterior end of 
the stomach to the vent with only one short forward turn 
of about a fourth the length of the body cavity, made a 
little way behind the stomach. Although the mucous sur- 
face of the intestine was at this time very rugose, show- 
ing a commencing complication of the digestive system, 
there was no trace of pyloric coeca. The intestine was 
filled with Cypris, Chydorus, Alona, Cyclops, etc. 
On the other hand, in a fish three and three-fourths 
inches long, showing the general characters of the adult, 
the intestine passed upward and backward from its 
origin, running without flexure the whole length of the 
body cavity (this part being covered with an immense 
number of pyloric coeca), then turned forward to the 
stomach, ran back from there about one-third of the way 
to the vent, then turned forward and ran a tortuous 
course beneath the stomach to the pericardial membrane 
and back again, also tortuously, two-thirds of the way to 
the vent. From this point it ran forward again to the 
stomach, and crossing to the left side, ran repeatedly 
backward and forward in the posterior part of the body 
cavity, making seven turns between the stomach and vent 
before opening, thus extending, in all, about eight times 
the length of the perivisceral cavity. This intestine was 
