SCIENTIFIC SUMMARY. 
561 
the electrical effects of a moveable conductor are due rather to 
the negative electricity of the earth than to the electricity of the 
atmosphere. 
3rd. It is not true, that in calms the electricity of the atmosphere is 
invariably positive, as the moveable conductor would lead us to 
think. — Vide Gomptes Rendus , lviii., 14. 
Production of Ozone by the Mechanical Action of Ventilating Machines . — 
In a paper which appeared not long ago in the Gomptes Rendus , M. 
Saintpierre records some remarkable facts in connection with the produc- 
tion of ozone by the mechanical propulsion of air. In the exit-tube of 
the blowing-machine of a foundry furnace he placed several bands of 
iodide of starch paper, and he exposed as many to the ordinary influence 
of the atmosphere ; and he found that whilst the latter underwent no 
change, even after five hours’ exposure, the former presented the charac- 
teristic violet tint in the course of about ten minutes. The staining cor- 
responded only to about 3° of the ozonometric scale. This was attributed 
to the fact that, as fast as the tint was developed, it was destroyed by the 
currents of air, an action which was afterwards found to produce such an 
effect by M. Saintpierre. May it not be possible to account for the results 
arrived at by supposing that the friction of the air against the surface of the 
tube developed electricity, and that this, in its turn, produced the ozone ? 
We fancy the action must be an indirect one, and do not see so much of 
the marvellous in it as M. Saintpierre would have us observe. — Yide 
Gomptes Rendus , lviii., No. 9. 
ZOOLOGY AND COMPARATIVE ANATOMY. 
Tubularia not Parthenogenous. — Professor H. J. Clark, of Harvard 
University, U.S., announces the discovery of the eggs of Tubularia. He 
has traced the development of the ovum in three distinct species, from its 
inception to the time of its escape, as a hydroid form, from the medusoid 
genital. He is not surprised that the egg has hitherto eluded the obser- 
vation of naturalists ; for its outlines are so faint that it might be put 
down as one of the tests of a first-class objective. Although he had 
obtained a glimpse of it with a Tolies’ ^-inch power, it was not till lie 
employed a ^-inch objective of the same maker, that he gained a clear 
and immutable view of it. He believes that in order thoroughly to under- 
stand the various steps in the development, it is necessary to admit the 
existence of a muscular layer in all these hvdrozoa. This layer consists 
of a thin longitudinally fibrillated tissue which intervenes between the 
outer and inner walls of the stem, disc, tentacles, and branching stems of 
the genitalia ; and whenever the latter pullulate to form a genital sac — a 
medusoid — all the cellular and muscular elements enter into the operation, 
and thus there arises at first a highly contracted triple-walled hernia, the 
outer wall of which consists of a single stratum of broad cells, each 
containing a large nucleus ; the middle wall or stratum forms the mus- 
cular layer ; and the innermost wall is made up of a single layer of very 
large prismatic cells. This is the first stage of medusoid development. 
Hardly, however, has the bud declared itself, before the ovigerous layer 
