The Digestive System 157 
pair form a fairly broad, moderately thick ring 
muscle next to the anus that is attached anteriorly 
to the pubis and posteriorly to the second hzmal 
process. When these muscles draw together they 
narrow or completely close the anal slit. The 
muscles of the other pair are broader but thinner, 
and extend in a general dorso-ventral direction. 
Anteriorly, above the cloaca, they are united with 
each other, but posteriorly they separate and, 
with the above ring muscle, are inserted on the 
second hemal arch. Judging from their attach- 
ment they widen the anal opening laterally. 
Tue HIsToLOGY OF THE ENTERON OF THE 
FLoripA ALLIGATOR 
_ It has long been known that the sea lamprey, 
Petromyzon marinus, during the spawning season, 
when the body is distended with eggs, takes no 
food, and that the digestive tract during this period 
shrivels up until it is reduced to a mere thread. 
This condition doubtless obtains in other forms as 
well, though it has not been actually observed by 
the writer elsewhere. 
A number of small alligators that were kept alive 
in the laboratory for a year or more caused the 
writer to wonder whether any very marked change 
had taken place in their digestive tracts during 
the months they took no food. 
In captivity, especially if the water in their tank 
