316 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 
is formed a fairly normal thorax. The left ribs of “Spine R.” 
and the right ribs of “Spine L.” are long and slender, and, passing 
backwards between the two spines, are normally inserted into a 
second well-developed sternum at the anticephalad end of the 
chick. 
With regard to the legs little need be said, as the two tails 
being well apart and the pelves normally developed, the four legs 
are at once seen to comprise a pair related to each pelvis. 
Fach sternum supports two corace-scapular arches with the 
attached wings. 
The arrangement of muscles and nerves makes it perfectly 
evident that the anterior pair of wings belong, the right to “ Spine 
R.” and the left to “Spine L. ;” while of the posterior pair, it is 
manifest that the wing to the right of the mesial plane is the left 
wing of “Spine R.,” and the other the right wing of ‘Spine L.” 
As already stated, there is but one umbilicus, and an examina- 
tion of the viscera shows, that in front of the vitelline duct the 
alimentary canal is single, and behind it double. In other words, 
cesophagus, gizzard, liver, and spleen are normal, and there is 
but one set; while from about two inches below the gizzard the 
alimentary canalis double. As there isa pair of pelves, there are, 
as one would expect, two sets of reproductive and urinary organs. 
The heart and large vessels are normal, and the anterior pair 
of wings is supplied by brachials, as if they were a normal pair. 
The two branches of the aorta unite and immediately re-divide to 
form an abdominal aorta for each pelvic extremity. The brachials 
for the two anticephalad wings are derived from the aorta, about 
the place where it is single. 
Perhaps the most interesting fact in the specimen is the fact of 
lungs, heart, liver, stomach, and spleen being single in their 
development, although the spinal cord is double from below the 
upper cervical region. These organs all derive their nervous 
supply from the tenth cranial or pneumogastrie nerve, and in their 
being single we have further evidence that, morphologically, they 
belong to the head, 
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