SCIENTIFIC SUMMAKY. 
107 
such is also the case on the West Coast, at Sierra Leone, Senegal, &c. — where 
these birds are, I believe, still more usually found — 1 cannot say ; but there is 
no doubt that in the large extent of country I have mentioned and explored 
for many years, and where these birds are common, copper is found very ex- 
tensively disseminated. I am unable to say whether the copper enters their 
system as a constituent of their food, as suggested by Mr. Church, but I 
believe it most probable that these birds are attracted by the bright green 
of the malachite, and swallow small particles of it with the gravel, &c. that 
they, in common with all birds, consume with their food.” 
The Phosphorescent Organs of Plater Noctilucus have been investigated 
recently by MM. Robin and Laboulbene, who state (“ Comptes Rendus,” 
T. 77, No. 8), that the light first appears in the centre, then spreads through- 
out. A yellow linear zone of adipose tissue at the exterior, at length 
becoming luminous, is yet not photogenic ; it only reflects the light pro- 
duced by the central part. But it does so, not only from its internal face but 
throughout its thickness, the action being favoured by the transparency and 
high refringent power of the fatty globules. The phenomena of dispersion 
and interference thus produced are the cause of the remarkable brilliancy 
appearing when the light from the centre reaches as far as this zone. As 
to the changes of molecular state in the tissue proper of the organ, the 
authors think the phosphorescent tissue produces a substance which slowly 
accumulates in the cells independently of all nervous influence, and of the 
same order with other secretions ; and that only the act by which it is dis- 
charged is voluntary. The principle rendering the cells luminous behaved 
like the noctilucine extracted by Phipson. The abundance of urates in the 
cells makes it probable that uric acid results from the photospheric decom- 
position of the preceding coagulable compound. The large number of 
tracheae in the apparatus is doubtless connected with the consumption of 
oxygen accompanying the phenomena. 
Multiplication of A caridce. — M. Megnin recently read an important paper 
on this subject, which has been abstracted by the “ Academy,” Nov. 1st 
[which journal, we are sorry to learn, is less likely to give us similar 
abstracts in its future numbers.] He asks — “ Whence come the legions of 
acaridae which make their appearance with such rapidity in decomposing 
fluids, and what becomes of them when their work of destruction is 
accomplished, and the matter on which they feed is reduced to the condition 
of a dry powder P These organisms, he remarks, have no wings to bear 
them from spots desolated by famine ; they have not the agility of ants to 
enable them to undertake long migrations; they have soft integuments 
which form but a very slight protection against external agents and their 
numerous enemies ; their eggs, relatively large, are not found in the dust of 
the atmosphere in company with the germs of moulds and infusory animal- 
cules ; and they do not possess, like the anguillules, rotifers, and the tardi- 
grades, the power of reviving after desiccation. Hence they are often 
referred to as illustrating the correctness of their views by those who hold 
the doctrine of spontaneous generation. But, according to Megnin, what 
happens in a colony of tyroglyphs, when the privation of food seems to 
promise them speedy destruction, is that all adult and aged individuals as 
well as the young hexapod larvae die, but the young and the octopodus 
