Sain ie 
o ie eee 
DD rrr eR NO eer ee 
i Se aS a es ee ee ae z - 
ise ie r si, — ec al .: - e 
Prof. Owen on the Class Mammalia. 177 
Art. XVII.—On the Characters, Principles of Division, and Pri- 
mary Groups of the Class Mammalia; by Professor Owen, 
F.RS., F.L.S., Superintendent of the Natural History Depart- 
S., 
ments in the British Museum.* 
(Concluded from page 18.) 
«| Shedd 
_ the brain is that part of the organization which, by its supe- 
_ development, istinguishes the Mammalia from all the in- 
ferior classes of VERTEBRATA; and it is that organ which I now 
Pose to show to be the one that by its modifications marks 
and most natural primary divisions of the class 
th some mammals the cerebral hemispheres are but feebly and 
Pattially connected together by the ‘fornix’ and ‘anterior com- 
wissure:’ in the rest of the class a part called ‘corpus callosum 
oma which completes the connecting or ‘commissural’ ap- 
Paratus, 
With the absence of this great superadded commissure ¢ is 
ted a remarkable modification of the mode of develop- 
ment of the offspring, which involves many other modifications ; 
ud the y body concerned in 
non-development of the deciduous c tae 
the hourishment of the progeny before birth, called ‘placenta ; 
ot tis Paper is cited from the Journal of the Proceedings of the Linnean Society 
ndon, Read February 17th and April 2ist, 1867. 
oe the Structure of ‘the Brain in Marsupial Animals,” Philos. Trans, 1887, 
8 
Sonn SERIES, VOL. XXV, NO, 74,—MARCH, 1988, 
23 
