300 
NATURE 
[NoveMBER 6, 1913 
symphysis of the Heidelberg jaw.’ On this hypo- | in regions where the respective models are present, 
thesis the common ancestor is conceived as possessing 
a simian mandibular symphysis, a massive jaw, large 
teeth, and probably a low forehead. From this 
ancestor the Heidelberg and Piltdown types may have 
come along diverging branches; the former leading 
up to Neanderthal man, the latter to H. sapiens. 
The author is strongly inclined to think that both 
the apes and Pithecanthropus have a low forehead, not 
because they are degenerate, but because they are 
immediately descended from monkeys. And even in its 
more plausible application to Neanderthal man, he 
views the degeneracy theory with considerable sus- 
picion. 
Untit quite recently holothurians (sea-cucumbers) 
were known from the older rocks merely by their hard 
spicules and plates, which were long ago identified 
in the Scottish Carboniferous. From certain very fine- 
grained Middle Cambrian beds in British Columbia 
there have, however, been obtained impressions of soft- 
bodied organisms which Dr. C. H. Walcott (Smith- 
son. Miscell. Collect., vol. Ivii., No. 3) identified as 
holothurians, under the generic names of Eldonia, 
Loggania, Louisella, and Mackenzia. But his deter- 
mination was not suffered to pass without criticism, 
and in Science of February 16, 1912, Dr. Lyman 
Clark expressed very strong doubts as to whether any 
of these genera are really holothurian, stating confi- 
dently that Eldonia is not. These criticisms are dis- 
cussed in the August number of The American 
Naturalist by Mr. Austin Clark, who arrives at the 
conclusion that, with the exception of Mackenzia, 
which is regarded as a zoantharian, the original 
identification is correct, two of the genera being 
assigned to the existing deep-sea family Elpidiide, 
while the third (Eldonia) represents an allied pelagic 
family. In bodily form the last-named type recalls 
a medusa, but the resemblance may probably be re- 
garded as a parallel adaptation to a free-swimming 
existence. 
In the October number of Bedrock, Prof. Poulton 
replies to Prof. Punnett’s criticism of the theory of 
mimicry in the July number of the same review. 
After pointing out that de Vries himself holds that 
small variations may be inherited and selected, he 
brings instances to show that such transmission does 
actually occur. The case of Acraea alciope is adduced 
as demonstrating that an incipient mimetic feature 
may arise as an occasional variation in one part of the 
area inhabited by a given species, which feature may be 
further developed in distinctness, and in the relative 
number of individuals possessing it, in the presence 
of a distasteful model occupying another part of the 
range of the mimicking species. These facts, it is 
contended, support the conclusion that ‘tthe mimetic 
pattern was attained by steps and not suddenly.” A 
more elaborate instance is afforded by Papilio polytes, 
with its two mimetic females. Here, apparently, the 
pigments of mimic and model have different genetic 
antecedents. By a detailed analysis of the patterns 
of the forms im question, and by a comparison of 
their numerical relation with the non-mimetic form 
NO. 2297, VOL. 92] 
rare, or absent, Prof. Poulton arrives at the conclu- 
sion that these forms have been derived from the 
ancestral condition by gradual stages, and that his 
opponent is not justified in the statement that natural — 
selection is non-existent in so far as concerns the — 
comparative numbers of the mimetic and non-mimetic — 
females of this species. 
The Scientific American for October 18 contains an — 
article on earthquakes and the Panama Canal, by — 
Mr. D. F. MacDonald, geologist to the Isthmian — 
Canal Commission. The recent occurrence of two 
earthquakes in the Isthmian zone has directed atten- — 
tion to a subject that might be of considerable import- 
ance with regard to the safety of the canal works. 
Mr. MacDonald, however. concludes that little danger 
is to be feared from earthquake disturbances (see 
Nature, vol. xcii., p. 174), and he gives two main 
reasons for his view. The first is connected with the 
geological structure of the isthmus. Though 
numerous small faults along the course traversed 
show that readjustments of the crust have taken 
place in times past, the district is one from which 
high mountains and all evidences of recent displace- 
ment are alike absent. Again, though a large num- 
ber of tremors are recorded every month by the 
Bosch-Omori seismograph at Ancon, the isthmus is 
entirely free from serious earthquakes. The seismic 
record of the isthmus dates from the Spanish con- 
quest, and during more than three centuries there 
have been only two earthquakes of any consequence. 
One in 1621 destroyed many buildings in Panama, 
while another in 1882 damaged several buildings and 
bridges, and in places threw the railway track out of 
alignment. But neither of these shocks, it is prob- 
able, would have damaged seriously even the most 
delicate parts of the canal. ; 
To Symons’s Meteorological Magazine for October 
Mr. R. C. Mossman contributes an article on cor- 
relations at St. Helena, the fifth of these interesting 
investigations. The results are not considered as con- 
clusive, but some suggestive resemblances and con- 
trasts have been disclosed. During the years 1893- 
1903 there was an undoubted relation between the 
rainfall in the vicinity of Fort William from January 
to March, and the mean temperature at St, Helena 
for the months May to August following, but from 
1904-11 the correlation breaks down. A relation could 
also be traced between the mean temperature at St. 
Helena during January to April and the mean baro- 
metric pressure at Punta Arenas (Magellan Straits) 
during the four months following, but during the last 
six years (1906-11) the results, for reasons given, 
were not very conclusive. With respect to tempera- 
ture at St. Helena and rainfall at Mexico City, the 
curves pursued the same course from 1892 to 1898, 
while from 1899 to 1909 they were the reverse of each 
other. It will probably be remembered that Dr. 
W. N. Shaw pointed out (NaTURE, December 21, 1905, 
“The Pulse of the Atmospheric Circulation”) an 
apparent connection between the seasonal variation 
of wind-force at St. Helena and the rainfall in the 
south of England. 
