No. 405.] THE INTESTINE OF AMIA CALVA. 721 
until the most caudal portion of the intestine is reached, and 
then, gradually, the muscle of the outer coat becomes less 
prominent, and at the end of the intestine the outside coat 
is made up of simply a thick band of connective tissue, with a 
very few small muscle bundles. There are so few of these that 
it does not seem that they have a very great part to play in the 
contraction of the intestine. The inner muscular coat under- 
goes no such decrease in size at the end of the intestine, but it 
does undergo some change, and at the last of the intestinal 
canal there is quite a marked decrease in the thickness of the 
coat, and the muscle fibres are not completely circularly ar- 
ranged, as in the rest of the intestine; but a rather complex 
arrangement of the muscle fibres has taken place, which differs 
much from the perfectly circular layer of fibres in the other 
places (Fig. 8. Perhaps this complicated arrangement is partly 
to compensate for the diminished longitudinal coat and also to 
take on some new functions, such as some of the muscles of 
the rectum perform in higher animals. 
Just entad of the inner muscular coat is a thick layer of 
connective tissue composed of fibres longitudinally disposed. 
This band of connective tissue is about as thick as, or some- 
what thicker than, the outside muscular coat and very dense. 
It does not seem to vary throughout the intestine, except at the 
end, where it gives place to a dense mass of connective tissue 
and isolated clumps of plain muscle bundles. At this place the 
mass of muscle and connective tissue extends uniformly from 
the epithelium to the inner muscular coat. It is about as thick 
as the two muscular coats together. With this exception the 
band of connective tissue is uniform throughout the intestine. 
It might be considered as an outside layer of submucosa, a sort 
of base upon which all the rest of the submucosa and mucosa 
Test. A dense connective-tissue band lying directly inside 
the muscular coats, but not so close to them as in Amia, has 
been described for several forms, as in the trout and Tinca vul- 
garis; this membrane has been called the membrana compacta 
Or stratum compactum. Doubtless the connective-tissue layer 
in Amia is homologous to this »emórana compacta. 
Especially above the spiral valve connective-tissue strands 
