67 
absorptive surface of the intestine). Many investigations 
have been made on their power of secreting enzymes, and 
the results obtained are confusing. Macallum* inyesti- 
gated the structures in Aczpenser, taking particular care 
to avoid the entrance of enzymes from the alimentary 
canal and pancreas, and found no certain evidence of a 
digestive action of their secretion on starch or proteid. 
Bonduoyt obtained the opposite results, finding the secre- 
tion of the ceca in many Teleosts to behave lke trypsin 
and to act strongly on starch and proteid. Macallum sup- 
poses that they represent the remains of a former series 
of digestive diverticula of the alimentary canal. These 
became restricted in most vertebrata to certain regions 
forming the digestive glands of the canal, but a variable 
number, however, persisted in Teleostomi as the pyloric 
ceca. 
The remaining portion of the intestine lies cn the 
ocular side of the body cavity. The duodenum passes 
into a tract of intestine which lies along the ventral and 
anterior walls of the body cavity to the left of the rectum. 
This is thrown into two S-shaped loops which terminate in 
the rectum. Near the anus the muscle layer becomes 
thicker, and the terminal portion of the rectum is also 
connected to the adjacent body wall by strands of connec- 
tive tissue. 
The Mesenteries are difficult to study on account of 
the convolutions of the intestine. They are best examined 
in a specimen well hardened with spirit. Two mesen- 
teric sheets appear to be present, though these may pos- 
sibly represent a single structure. One takes crigin from 
the dorsal and posterior walls of the body cavity in the 
* Jour. Anat. and Phys., vol. xx., pp. 604-636, 1886. 
+ Arch. Zool, Exper., vii., pp. 419-460, 1899. 
