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NovEMBER 27, 1913] 
be practically put out of court. The interpretation 
which at present holds the field is that which attri- 
butes the resemblances in colour, with their correlated 
geographical modifications, to the action of mimicry, 
either Batesian or Miillerian. 
Mimicry. 
Prof. Poulton opened what was intended to be a 
discussion on mimicry, but the opposition did not 
appear to be present in force, and there was not a 
real debate. Prof. Poulton directed attention to the 
injuries actually seen to be inflicted on butterflies by 
wild birds, and laid stress on disabling injuries, such 
as the loss of a whole wing or the head, indicating 
that the insect had not escaped, but was abandoned 
by the enemy. Such injuries are especially charac- 
teristic of the great groups which supply the models 
for mimicry, e.g. the Danainz and Acreinz in Africa. 
The crops of enormous numbers of birds have been 
examined and stated to contain no remains of butter- 
flies, but Prof. Poulton contended that the force of 
this requires reconsideration in the light of the recent 
work of Mr. C. F. M. Swynnerton in south-east 
Rhodesia. Pellets thrown up by captive insectivorous 
birds had been collected by Mr. Swynnerton, and were 
exhibited at the meeting, together with examples of 
butterflies belonging to the same species as those 
devoured. These pellets, when broken up, would 
have come under the well-known classification, ‘‘ insect 
débris, unrecognisable,"’ but Mr. Swynnerton has 
shown that no safe conclusion as to the nature of 
the pellets can be drawn except after microscopic 
examination sufficiently minute to detect the presence 
of lepidopterous scales and their sockets. The objec- 
tion against the origin of mimicry by small variations 
was met by the exhibition of mimetic females of 
Acraeaalciope, from the west coast of Africa and from 
western and eastern Uganda. In the first series the 
female Acrazeas mimic the brown male (and in some 
species the female also) of the Acrzine genus 
Planema, in eastern Uganda, they mimic the male of 
P. macarista, and the male and female of P. poggii, 
with an orange bar across the fore-wing and a white 
bar across the hind-wing. In western Uganda the 
transitional forms are found, some of the female 
Acrzas exhibiting a pattern similar to that of the 
west coast form, while others show an incipient white 
bar across the hind-wing, but the fully formed eastern 
mimic is not known to occur in this locality. In the 
intermediate zone of country the intermediate varia- 
tion is met with, connecting the western mimic with 
the eastern. Prof. Poulton cited examples of mimicry 
between the genera of certain African Nymphalines, 
pointed out the development of secondary resemblances 
between the mimics, and exhibited series of models 
and mimics taken in one sweep of the net in Lagos, 
thus showing that the mimics actually fly in the com- 
pany of their models. He also showed illustrations 
and specimens of a few cases of mimicry in temperate 
North American butterflies, and pointed out what he 
believed to have been the evolutionary history. If 
this history be correct, then it is impossible to explain 
the resemblance as due to the influence of environ- 
ment, because recent invaders from the Old World 
into this region have caused the mimetic modification 
of indigenous species. According to the theory of 
environment the invaders and not the residents ought 
to have been modified. 
Prof. van Bemmelen remarked that mimetic re- 
semblances required to be very carefully analysed. 
He had attempted to show that some of the patterns 
on the wings of butterflies were old and others new, 
NATURE 
387 
planation is attended by such extreme difficulty as to | traceable to a pattern existing far back in phylogeny, 
and that the subject should be further investigated 
from this point of view. 
Other Papers on Lepidoptera. 
Sir George Kenrick discussed the classification of 
the Pierines, and Mr. G. T. Bethune-Baker exhibited, 
with the aid of the epidiascope, specimens showing 
changes in pattern, colour, and structure (e.g, the 
genitalia) in the Ruralidze which lead him to conclude 
that pattern is very generally correlated with structure. 
Mr. G. D. H. Carpenter communicated observations 
on the enemies of “‘protected’’ insects with special 
reference to Acraea zetes. Such insects, “ protected," 
for instance, by their distastefulness from the attacks 
of vertebrates, are preyed upon by predaceous insects 
and parasites. 
The Ascidian Diazona violacea. 
Prof. Herdman exhibited specimens of this com- 
pound Ascidian, which he had dredged recently in the 
Hebrides. When alive the colony was bright green, 
but when preserved in alcohol it became violet in 
colour. Other specimens preserved in formalin re- 
tained their green colour. Green specimens dredged 
from deep water changed their colour in sunlight, 
and finally acquired a violet tint. The green colour 
is not due to chlorophyll, but to an allied pigment 
which has been named syntethein. The green 
Hebridean and the violet Mediterranean form are un- 
doubtedly the same species. 
Early Evolution of the Amphibia. 
Mr. D. M. S. Watson destribed the osteological 
characters of the Amphibia of Carboniferous, Per- 
mian, and Triassic formations, and concluded that, 
taken as a whole, the rhachitomous Amphibia of the 
Permian are intermediate in their structure, as they 
are in time between the embolomerous Carboniferous 
and the stereospondylous Triassic types, and it would 
seem that each of the three groups is to be regarded 
as ancestral to that which follows it. The almost 
absolute identity of the skulls of Pteroplax, an embolo- 
merous Amphibian of Carboniferous type, and Sey- 
mouria, which has the most primitive skull of any 
known reptile, seems to show definitely that the 
reptiles did arrive from that group of Amphibia, pre- 
sumably in early Carboniferous or Upper Devonian 
time. Mr. Watson suggested that the development 
of the bi-condylar articulation of the skull of Amphibia 
is to be correlated with the increasing depression of 
the skull, and is a characteristic Amphibian feature. 
Prof. Elliot Smith referred to the difficulty presented 
by the Amphibian cerebral cortex in regard to the 
phylogeny of the mammalia. He pointed out that in 
Petromyzon the cerebral cortex is rudimentary, in 
Selachians it is more highly developed, and in Dipnoi 
is almost as well developed as in reptiles, but in 
Amphibia is degenerate and feebly efficient. But 
Amniota must have gone through some Amphibian 
ancestry. It is now evident that the retrogression 
of the Amphibian cortex must have taken place since 
the reptiles branched off the Amphibian stem. 
Metamorphosis of the Axolotl. 
Mr. E. G. Boulenger gave an account of the experi- 
ments which he had recently conducted on the meta- 
morphosis of the Mexican axolotl (Amblystoma 
tigrinum). He concluded that the axolotl will, with 
a few exceptions, transform if placed under special 
conditions which force it to breathe air more fre- 
quently than usual; that starvation, irregular feed- 
ing, and temperature have no influence on the meta- 
and he suggested that some resemblances might be j morphosis; that elimination of oxygen from the water 
NO. 2300, VOL. 92] 
