98 NATURE 
with iron girders surrounding the pipe. The whole 
subject is so new that we have to feel our way in 
this investigation. Here in Ottawa, three hundred 
miles from the nearest sea-coast, we have in a general 
way correlated microseisms recorded by the seismo- 
graph with the storms along the Atlantic coast from 
Cape Hatteras to St. John’s, Newfoundland, a dis- 
tance of 1500 miles, so that for an exhaustive study 
there should be quite a number of undagraphs in- 
stalled. However, a beginning has been made at 
Chebucto, distant in an air-line about 620 miles from 
Ottawa, and the results will be published as soon as 
available. 
Orro Krorz. 
Dominion Astronomical Observatory, 
Ottawa, September 5. 
Geographical Distribution of Phreatoicus. 
Tue occurrence of the isopod Phreatoicus in a 
fresh-water stream near Cape Town, in South Africa, 
as recorded in your issue of June 12 by Mr. Keppel H. 
Barnard, is of very considerable interest from the 
point of view of the geographical distribution of the 
group. Since I described the first species of the 
genus in 1884 our knowledge of this group has grown 
very rapidly, and there are now known three species 
of Phreatoicus in New Zealand, two subterranean and 
one from surface waters, and several species grouped 
under allied genera from Australia and Tasmania. 
The genus is shown both by its generalised character 
and by its distribution to be an ancient one. I have 
long considered that it is probably a fresh-water form 
that has developed in. subantarctic lands, and its dis- 
covery in South Africa seems to confirm this. In 
New Zealand it appears to be confined to the more 
southerly portion, but it was rot found in the: sub- 
antarctic islands to the south of New Zealand when 
these were visited in 1907. It should, however, be 
looked for in other subantarctic islands, particularly 
St. Paul and Amsterdam Islands in the Indian Ocean, 
and the Falkland Islands and adjoining parts of: South 
America. Cuas. CHILTON. 
Biological Laboratory, Canterbury College, N.Z., 
August 7. 
The Characters of Hybrid Larve obtained by Crossing 
Different Species of the Genus Echinus. 
I WAVE carried out this summer hybridisation ex- 
periments on certain species of echinoids, and, in 
view of the interesting condition in which this inquiry 
was left last year by other workers, I venture to 
think that my results may be worth recording. 
In torr, Shearer, De Morgan, and Fuchs, as the 
result of three seasons’ crossing experiments at Ply- 
mouth, stated (Journal M.B.A., ix., 2) that the 
hybrids between Echinus miliaris, on the one hand, 
and E. esculentus or E. acutus, on the other, showed, in 
respect of certain larval characters, a purely maternal 
inheritance. In 1912 the same workers, in a letter 
to Nature, and later in The Quarterly Journal of 
Microscopical Science, published the result of their 
latest experiments, which was, briefly, that when E. 
miliaris was mother the inheritance was paternal. 
They found one culture which was_ exceptional. 
Debaisieux, working at the same time, and inde- 
pendently, first in London upon Plymouth material, 
and afterwards at Millport, obtained substantially 
identical results. These results he expressed in terms 
of dominant and recessive characters in the larvae. 
This disparity between the results of 1912 and those 
NO. 2291, VOL. 92] 
[SEPTEMBER 25, 1913 
of former years raised a number of interesting ques- 
tions, and made urgent a repetition of the experiments 
—a work that at the suggestiom of Prof. E. W. Mac- 
Bride (whose encouragement and advice | gratefully 
acknowledge) I undertook to perform. 
The species used by me were those mentioned 
above, and the symbols, M and m, E and e, A and a, 
may be used to represent the @ and d gametes 
respectively of each of them, the zygotes being then 
written Mm, me, Em, Ee, &c. The larval characters, 
the inheritance of which was studied, were the green 
pigment masses of Mm plutei, on one hand, and, 
on the other, the posterior pair of ciliated epaulettes 
and the posterior pedicellaria of Ee and Aa plutei. 
Debaisieux found the first of these ‘“recessive,’’ the 
other two ‘‘ dominant.” 
In London I succeeded in raising cultures of Mm, 
Em, and Am plutei only, the reciprocal crosses failing 
for want of ripe males. Plymouth sea-urchins were 
used, and sea-water from Lowestoft. The hybrids, 
without exception, showed maternal characters. But 
in these crosses the dominant characters of Debaisieux 
were also maternal characters. I accordingly made 
further experiments at the Millport Marine Biological 
Station during July and August, using E. miltaris 
and E. esculentus only for my crosses. 
After many failures, four healthy cultures of the 
Me cross were reared, one culture to a stage at which 
the anterior epaulettes were formed, the other three 
to the stage of metamorphosis. In the first culture 
green pigment was absent from all the larve 
examined; in the other three cultures all the indi- 
viduals (132) had posterior epaulettes, eighty-one had 
the posterior pedicellaria, none had green pigment. 
The reciprocal cross 
agreed in its charac- 
ters with the one 
made in London. 
There was a very 
notable difficulty in 
making the Me cross 
—a difficulty which 
would seem to be in- 
trinsic, and uncon- 
nected with any 
defect in the egg, 
because it has  oc- 
curred again ané 
again in experiments . “%. 
in which the Mm i 
and Ee controls have 
poth yielded good 
cultures ot plutei. 
The E£. miliaris used 
as parents were 
small, and the 
ovaries contained a 
large proportion of : 
unripe eggs; but a majority of the apparently ripe 
eggs developed, when fertilised with sperm of their 
own species, while only a small proportion developed 
when E. esculentus sperm was used. 
The mortality in the Me cultures finally examined | 
was unusually low after the blastula stage, and could 
be assessed with considerable accuracy on account of 
the small number of individuals in a culture. Differ- 
ential mortality would seem then to be improbable as 
accounting for the final character of a culture. 
The sketch shows a hybrid pluteus (Em) as seen 
from the left side: a, anterior epaulettes; # posterior 
epaulette; pp, posterior pedicellaria. 
H. G, NEwrTu. 
Zoological Department, Imperial College of 
Science and Technology. 
a ae ee 
a) 
