120 
ORIGINAL ARTICLES. 
were corresponding structures, and that the articulation of the head 
of the mammalian rib to the body of the vertebra was that which 
corresponded to the attachment of the piscine rib. 
To accept this theory involves the assumption that the exact point 
of origin of a process or rib from the vertebra, and the source of its 
ossification are matters of primary morphological importance. But 
even with mammalian ribs there is a considerable amount of variety 
in the method of attachment to the vertebrae. Thus the posterior 
ribs in the cetaceans are attached only to the transverse processes; 
and these processes, according to Muller, are neither the ordinary 
piscine nor mammalian transverse processes. Ordinarily, the head 
of the mammalian ribys attached to the origin of the arch, a circum¬ 
stance which is in itself adverse to Muller’s theory ; but the posterior 
ribs in the Seal, and probably also in some other carnivora, articulate 
with centra; and in the Echidna, whose ribs have no costo-transverse 
articulation, Prof. Huxley remarks that “ the head of every rib is 
attached to the centrum, or below the neuro-central suture, and in 
the neck this suture lies between the upper and lower transverse pro¬ 
cesses —a remark which I have verified, with the slight exception 
that in the specimen which I examined, the last pair of ribs was 
attached quite above the neuro-central suture. Hence it appears 
that the points of attachment of ribs to vertebrae are not of any 
great morphological importance. Neither shall we find that the 
source of ossification of processes, although it has a certain import¬ 
ance, is of primary significance. There are caudal vertebrae in many 
mammals, the Hog for example, entirely ossified from the centra; 
which send upwards very small pairs of processes forming the rudi¬ 
ments of neural arches, and outwards small transverse processes. 
Whatever we may think of the latter, we cannot fail to see that there 
is a greater amount of correspondence between the former and neural 
arches than can be counterbalanced by the fact of their being pro¬ 
ductions of the centrum and not autogenous. In fishes and reptiles 
there are other varieties in the source of ossification of the neural 
arch which need not be here enumerated.* So also the anterior part 
of the upper jaw in man indubitably corresponds to the intermaxillary 
bone in any other mammal, although, except in cases of cleft palate, 
it is ossified, as M. Em. Eousseau has shown, from the maxillary. In 
the face of these evidences of variability in the sources of processes 
it is impossible to admit that the mere circumstance that the trans¬ 
verse processes in the posterior part of the Dolphin’s vertebral 
column arise from separate centres of ossification, and are attached 
to the sides of the bodies of the vertebrae, affords sufficient ground for 
* On this subject and on the attachment of ribs, see Prof. Huxley’s note, “ On 
the development of the Ossified Yertebral Column,” appended to his lecture “ On 
the Theory of the Vertebrate Skull.” Royal Soc. Proc. Nov. 18, 1858. 
