582 TRANSACTIONS OF SECTION H. % 
c 4 
power of adaptation, and from its South African home began to wander through- 
out the world. In turn the Prototherian and Metatherian types of brain were 
tried before the more adaptable scheme of the Hutherian brain was evolved. 
‘he group of lowly Insectivora, including such creatures as Moles, Hedge- 
hogs, and Shrews, persists to the present time to reveal the nature of the earliest 
Eutherian brain. 
The Insectivora have been able to persist in competition with more advanced 
mammals by reason of their small size, and the development of manifold varieties 
of protective specialisations and the adoption of habits to ensure their safety. 
In their spread throughout the world they eventually came to occupy practically 
the whole earth, with the remarkable exception of the Australasian and, except 
for a short time, South American regions, where their predecessors, the Meta- 
theria, found a haven of refuge, which saved them from the extinction that would 
inevitably have been their tate if they had had to struggle for existence in 
competition with the more nimble-witted Eutheria, endowed with a superior 
type of brain.** 
Among the Insectivora there is one group—perhaps worthy of ordinal dis- 
tinction, the Menotyphla of Haeckel—which is of peculiar interest to the student 
of Primate and human genealogies. 
This group includes the Oriental Tree-Shrews and the African Jumping- 
Shrews. ‘The latter (Macroscelidide), living in the original South African home 
of the Mammalia, present extraordinarily primitive features, linking them by 
close bonds of aflinity to the Marsupials. The Tree-Shrews (Tupaiidz), however, 
which range from India to Java, while presenting very definite evidence of 
kinship to their humble African cousins, also display in the structure of their 
pin positive evidence of relationship to the stem of the aristocratic Primate 
phylum. 
I need not discuss the evidence for these views, because it has recently been 
summarised most excellently by Dr. W. K. Gregory ** of New York. 
It will suffice to point out that, quite apart from the striking similarities 
produced by identical habits and habitats, there are many structural identities, 
not directly associated with such habits, which can be interpreted only as evi- 
dences of affinity. 
These Tree-Shrews are small squirrel-like animals which feed on ‘ insects and 
fruit, which they usually seek in trees, but also occasionally on the ground. When 
feeding they often sit on their haunches, holding the food, after the manner of 
squirrels, in théir forepaws.’** They are of ‘lively disposition and great 
agility.’*t ‘These vivacious, large-brained, little insectivores, linked by manifold 
bonds of relationship to some of the lowliest and most primitive mammals, 
present in the structure of their skull, teeth, and limbs undoubted evidence of 
a kinship, remote though none the less sure, with their compatriots the Malay- 
sian Lemurs; and it is singularly fortunate for us in this inquiry that side by 
side there should have been preserved from the remote Eocene times, and possibly 
earlier still, these insectivores, which had almost become Primates, and a little 
primitive lemuroid, the Spectral Tarsier, which had only just assumed the 
characters of the Primate stock, when Nature fixed their types and preserved 
them throughout the ages, with relatively slight change, for us to study at the 
present day. 
Thus we are able to investigate the influence of an arboreal mode of life 
in stimulating the progressive development of a primitive mammal, and to 
appreciate precisely what changes were necessary to convert the lively, agile 
Ptilocercus-like ancestor of the Primates into a real Primate. 
In the forerunners of the Mammalia the cerebral hemisphere was pre- 
dominantly olfactory in function; and even when the true mammal emerged, 
and all the other senses received due representation in the neopallium, the 
animal’s behaviour was still influenced to a much Ha he extent by smell impres- 
sions than by those of the other senses. 
This was due not only to the fact that the sense of smell had already installed 
18 Vide Avris and Gale Lectures, op. cit., supra. : 
19 «The Orders of Mammals,’ Bull. Amer. Mus. Nat. Hist., vol. xxvii., 1910, 
p. 321. 
*” Flower and Lydekker, Mammals, Living and Txtinct, 1891, p. 618. 
21 W. K. Gregory, op. cit., p. 269, and pp. 279, 280. 
