Miscellaneous. 263 
derm. When the blastoderm has thus given birth to the mesoderm 
and endoderm, it persists as a simple cellular layer around the layers 
which arise from it, and constitutes the ectoderm. In short, the 
primitive blastoderm is alone the origin of the three layers ; the cells 
of which it is composed multiply rapidly, and group themselves in 
two different ways; some remain at the periphery and will form 
part of the ectoderm, while the rest penetrate into the ovule and 
represent a meso-endoderm, which will differentiate into the two 
final inner layers. 
One of the most important facts is the diffuse genesis of the meso- 
derm by almost the entire blastoderm ; a second is the double origin 
of the endoderm, the two original zones being separated by a vast 
space. These two peculiarities taken together are really charac- 
teristic, for we do not meet with them in the condensed developments 
of the rest of the Coelomata. Finally, a concluding phenomenon of 
great value is presented by the enteron or primitive intestine, which 
hollows itself out in the interior of the embryo without in any way 
proceeding from a gastrular invagination, and does not even present 
a trace of such a primordial origin ; here, again, is a contrast to the 
condensed developments of the other Coelomata. At the present ‘ 
moment I am continuing my investigations and extending them to 
the Podophthalmata ; I shall shortly have occasion to show that they 
exhibit the same phenomena as the Edriophthalmata, and that the 
blastodermic depressions, considered by divers authors, by Reichen- 
bach and Bobretzky among others, as gastrular invaginations, have 
not, in reality, such a significance.—Comptes Rendus, tome exiil. 
no. 24 (December 14, 1891), pp. 868-870. 
A new Mode of Respiration in the Myriapoda. By F.G. Srncrarr 
(formerly F. G. Huarncore), M.A., Fellow of the Cambridge 
Philosophical Society. 
The Scutigeride respire by means of a series of organs arranged 
in the middle dorsal line at the posterior edge of every dorsal scale 
except the last. 
Each organ consists of a slit bounded by four curved ridges, two 
at the edges of the slit. and two external to the latter. The slit 
leads into an air-sac. From the sac a number of tubes are given 
off; these tubes are arranged in two semicircular masses. The ends 
of the tubes project into the pericardium in such a manner that the 
ends are bathed in the blood and aérate it just before it is returned 
into the heart by means of the ostia. In the living animal the 
blood can be seen through the transparent chitin of the dorsal 
surface surrounding the ends of the tubes ; and in the organ and 
surrounding tissues cut out of a Scutigera directly it is killed, the 
bleod-corpuscles can be seen clustering round the tube ends. If the 
mass of tubes of a freshly killed specimen are teased out under the 
microscope in glycerine, they can be seen to be filled with air. The 
tubes each branch several times. Each tube is lined with chitin, 
which is a continuation of the chitin of the exo-skeleton. Each 
tube is also clothed with cells, which are a continuation of the 
hypodermis. ‘The tubes end in a blunt point of very delicate chitin. 
