The peculiar feature in the population of the whole series
of secondary strata, was the prevalence of numerous and
gigantic forms of Saurian reptiles; Many of these were
signed with especial reference to each other's peculiar condition." With respect to the final cause of these peculiarities, he conjectures that they have relation to an inferior condition of the brain and nervous system in the Marsupialia; and considers the more protracted period of viviparous utero-gestation in the higher orders of Mammalia to be connected with their fuller development of the parts subservient to the sensorial functions; the more simple form and inferior condition of the brain in Marsupialia, being attended with a lower degree of intelligence, and less perfect condition of the organs of voice.
As this inferior condition of living Marsupialia shows this order to hold an intermediate place between viviparous and oviparous animals, forming, as it were, a link between Mammalia and Reptiles; the analogies afforded by the occurrence of the more simple forms of other classes of animals in the earlier geological deposites, would lead us to expect also that the first forms of Mammalia would have been Marsupial.
In a recent letter to myself; Mr. Owen adds the following interesting particulars respecting the physiology of this remarkable class of animals. "Of the generality of the law, as regards the simple unconvoluted form of the cerebrum in the Marsupials, I have had additional confirmation from recent dissections of a Dasyurus and Phalangista. With an organization defective in that part which I believe to be essential to the docility of the horse, and sagacity of the dog, it is natural to suppose that the Marsupial series of warm-blooded quadrupeds would be insufficient for the great purposes of the Creator, when the earth was rendered fit for the habitation of man. They do, indeed, afford the wandering savages of Australia a partial supply of food; but it is more than doubtful that any of the species will be preserved by civilized man on the score of utility. The more valuable and tractable ruminants are already fast encroaching on the plains where the kangaroo was once the sole representative of the graminivorous Mammalia.
"It is interesting, however, to observe, that the Marsupials, including the Monotremes, form a very complete series, adapted to the assimilation of every form of organic matter; and, no doubt, with enough of instinctive precaution, to preserve themselves from extermination, when surrounded with enemies of no higher intellectual powers than the Reptilia. It would, indeed, be a strong support to the consideration of them as a distinct ovoviviparous sub-class of Mammals, if they should be found as hitherto, to be the sole representatives of the highest class of Vertebrata, in the secondary strata."—R. Owen.
