none Oe, le 
January 27, 1923] 
The Distribution of Life 



‘ 
Wegener's 
ONE of the most important results of the accept- 
. * ance of Wegener’s theory of the palaogeo- 
graphy of the world would be the simplification of the 
facts of the Permo-Carboniferous glaciation of 
ustralia, India, South Africa, and South America 
by bringing the glaciated areas together into one 
single glaciated region. It is undoubted that if this 
were done much of the difficulty of accounting for the 
‘simultaneous glaciation of regions so diverse in lati- 
tude would disappear. Considerable interest, there- 
fore, attaches to the recent discussion on Wegener's 
hypothesis, which was held before the Royal Society 
of South Africa, for its bearing on this important 
al of the subject. 
: general attitude of the geologists who took 
‘part in the discussion was one of suspended judg- 
ment. It is admitted that the folded ranges of the 
Sierras of Buenos Aires appear to be of similar age 
and structure to those of the southern folded belt of 
the Cape Province, and would be brought into fairly 
accurate alignment if the South American coast were 
fitted into the African coast after the manner of 
Wegener’s map of Carboniferous land distribution, 
but it was held that this might be accounted for in 
; other ways more in accord with the known 
facts of geology. On the other hand, the very close 
and detailed homology of the Tertiary deposits of 
Grahamland and Patagonia as described by Gunnar 
Andersson forms one of the most relevant pieces of 
combined geological and palzontological evidence from 
the southern hemisphere in support of the theory. 
Discussing the zoological evidence, Mr. K. H. 
Barnard concludes that the zoologist, far from being 
ble to help in formulating an explanation of the 
palzogeographical history of the continents, was, in 
reality, entirely dependent on the geophysicist and 
logist, and that in some cases the facts of present- 
iy distribution were capable of interpretation in 
terms either of a far-reaching equatorial Gondwana- 
land or a compact polar Gondwanaland. There is 
e to choose, for example, between Watson's theory 
of the dispersal. of acarid snails from S.E. Asia 
equatorial Gondwanaland} and Hedley’s theory of 
their origin in Antarctica [polar Gondwanaland], 
nd whichever geological theory best explains the 
eogeographical changes must be used as a basis by 
zoologists. Similarly, if the ancestors of the fresh- 
water crayfishes originated in an arm of the Indo- 
Pacific which gradually penetrated into polar Gond- 
analand in pre-Jurassic times, the same results 
Bs follow as those sketched out by Ortmann for 
post-Jurassic times. The distribution of Peripatus, 
on the other hand, is apparently best explained on the 
polar Gondwanaland hypothesis. If the distribution 
the species of Peripatus is plotted on a polar pro- 
ection map, it is remarkable that the Peripatopside, 
the more specialised group, occupy a central position, 
while the Peripatide, the more primitive, are peri- 
al. The most important zoological evidence in 
‘support of Wegener's theory is provided by the 
isopod, Phreatoicus. At the present time it is found 
‘in Australia, Tasmania, New Zealand, and South 
Africa. There is the closest possible likeness between 
a of the Australian species and the Cape form. 
In Australia there is also a fossil species of Triassic 
age, which provides almost positive proof that the 
nimal was not only palwogenic, but also austrogenic, 
nd that the regions where it exists to-day were once 
_in the very closest relationship to one another. 
Dr. Peringuey, discussing the entomological evi- 
dence, concludes that the present distribution of 
insects is as readily accounted for by the geological 
NO. 2778, VOL. 111] 







































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NATURE 
13! 
in the Southern Hemisphere, and its Bearing on 
Hypothesis. 
theories now obtaining as by Wegener's hypothesis, 
and believes that the latter will receive little if any 
support from entomology. He agrees that the key 
will be found in ary By tet but is forced to 
admit that the evidence from fossil insects is at 
present too inadequate to be of value. Discussing 
the special case of the Coleopteron genus Carabus, 
first found in Jurassic times, Dr. Peringuey points 
out that it is unknown in the Old World south of the 
Sahara, but one species occurs in St. Helena and seven 
in Chile. He regards the St. Helena and Chilian 
forms as survivals from an equatorial Gondwanaland, 
in isolated spots at high altitudes, and not as evidence 
of the former connexion of South America and St. 
Helena, in their present form, with South Africa, 
where the genus is absent, or with Australia, where the 
genus is unknown but where its vitality should have 
ensured its success. On the other hand, the nearest 
ally of Carabus, the genus Calosoma, has three 
species in South Africa, three in Australia, one in the 
Galapagos Islands, and one in Patagonia, a distribu- 
tion which seems to support the unity of the con- 
tinents alleged by Wegener. In Australia there is a 
group of large Curculionide, one of the families of 
Coleoptera, which so much resembles a purely South 
African group of the same family that, at first sight, 
the two might be taken to represent the same stock 
in two now widely separated continents. Dr. 
Peringuey, however, regards this as a case of con- 
vergence. 
Prof. Compton regards the botanical evidence as 
completely opposed to Wegener’s theory. The per- 
fection of the means of dispersal of plants renders 
many of the facts as to the modern distribution of 
ancient groups (Cryptogams) almost valueless as an 
indication of former land connexions. Recent phyla 
only, especially the Angiosperms, can be relied on. 
The Angiosperms arose during Cretaceous times, and 
most modern families are represented in the Eocene. 
The Wegener hypothesis contemplates a wide dis- 
ruption of South Africa and Australia in the Jurassic 
epoch, but South Africa and South America were only 
separated by a very narrow strait at the end of the 
Cretaceous period. Yet the floristic resemblances 
between temperate South Africa and South America 
are much less conspicuous than between temperate 
South Africa and Australia. The floristic relation- 
ships between South Africa, South America, and 
Australia are best explained as being due to lateral 
migration, perhaps in the warmer Miocene, from a 
comprehensive tropical belt of vegetation, containing 
most of the great Angiosperm families, which stretched 
round the world except the Pacific. The south 
temperate floras, therefore, are linked through the 
tropics except for South America and New Zealand, 
which certainly seem to have been connected by land, 
via Antarctica, in the Miocene. The modern dis- 
tribution of the Rutacez is an excellent instance of 
the progress of migration southwards as well as north- 
wards from this tropical belt, and tentative explana- 
tions of the distribution of the Proteacee and Res- 
tionaceee may be given on the same lines. Dr. Du 
Toit regards the paleobotanical evidence as too frag- 
mentary for botanists to do more than make guesses 
at the probable origin of the South African flora. 
The net result of this interesting discussion is to 
emphasise the importance of further work on the 
paleontology of the southern hemisphere. In that 
direction alone will be found the key to the correct 
interpretation of the known facts of the present day 
distribution of animals and plants, and of the paleo- 
geographical changes which fave taken place. 
