Severin and Severin—Anatomical Studies of Cimbex. 51 
[“valvule rectale ,> of Balbiani, “sphincter de Vintestine grele” 
of Van Gehuchten (15)] of the anterior ileum. This valve 
prevents the material in the hind-intestine from passing back 
into the ileum after it has once entered the rectum. 
Rectum :—The rectum shows a marked histological difference 
from the ileum. Near the boundary between these two di¬ 
visions of the hind-intestine, the cells of the ileum become 
smaller and pass abruptly into the much reduced cells of the 
rectum. The walls of the entire rectum, with the exception of 
the rectal glands, are thrown up into irregular internal folds. 
The cells, with cell boundaries indiscernible, are represented 
chiefly by their nuclei. These cells and the folded nature of 
the rectum show a marked similarity to the structure of the 
oesophagus and crop. 
We are deeply indebted to Professor William S’. Marshall., 
who has given us valuable assistance in reading the manuscript 
with us. This work was undertaken at his suggestion and car¬ 
ried out in his laboratory. 
Zoological Laboratory, 
University of Wisconsin, 
BIBLIOGRAPHY. 
1. Ahglas, J. : Observations sur les metamorphoses internes 
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