1859. | CONVOLUTIONS IN BIRDS. 307 
enumeration and deseription of the intestinal convolutions as they 
oecur in the numerous orders and families of birds, because this will 
be dene elsewhere. 
The Table (pp. 308, 309) contains, ina condensed form, an account 
of the principal modifications of the intestinal folds, and the diagram 
(Plate XXXIL.) shows the affinities, or, to speak more cautiously, the 
convergent similarities, of all the principal families, as they are 
suygested merely by a study of their intestinal arrangements. The 
birds will be discussed only from this point of view in order to test, 
and to draw attention to, the taxonomic value of those characters 
which are exhibited by the modes in which the mid-gut is stowed away 
in the abdominal cavity. 
Many of these simuarities are perhaps merely coincidences, and 
in this case can have no taxonomic significance; but if these simi- 
larities coincide with those of several other organic characters, they 
are entitled to a higher rank as indicating not convergence but 
common descent of those birds in which they persistently occur. 
There seems to be a sort of belief prevailing that the intestinal 
convolutions are very variable and unreliable in the same species, 
that they are a matter of accident ; but, on the contrary, I have found 
them constant to an astonishing exteat, not only in the same species 
but in many large families. Of course secondary shortening and 
widening of the gut (owing to the assumption of (rugivorous habits) 
may reduce the number of loops, and may render the original 
ar rangement quite untraceable, as in, e. g., Carpophaga, Rhamphastus, 
Manucodia. When a bird has acquired strictiy piscivorous habits, 
the gut is cousiderably lengthened and narrowed, and may, just as in 
Pandion and in Haliaetus, render the old formation quite unrecog- 
nizable. These are, however, exceptions, which are not numerous ; 
as a rule the lengthening of the pre-existing loops and the additional 
intercalation of new ones does not disturb the typical formation, but 
rather throws interesting lights upon the lives of new departure along 
which certain birds have become developed, e. g., the Alcedinidee 
from a Coraciine stock, now modified through the acquisition of 
carnivorous and piscivorous habits. 
In the following Table the order adopted is one of mere con- 
venience, without necessarily indicating near relationship. The 
second column contains the number of principal loops; this can 
best be ascertained by spreading the intestine out on the table with- 
out tearing the mesenteric connections. The next three columns 
refer to the 2nd, 3rd, and 4th principal loops: 7 means that the loop 
in question is a right-handed one, like the duodenum ; / that it is 
retrograde, or left-handed ; o signifies that the loop is open; e/ that 
it is closed. The last column indicates in a few words the type of 
formation. 
The diagram (Plate XXXII.) requires some explanation. All 
the birds of which the names are written inside the inner of the 
two concentric circles are on the whole orthoccelous, whilst those 
placed between the two concentric circles are cycloccelous ; of the 
latter, the underlined families are telogvrous, the others mesogyrous. 
