SCIENTIFIC SUMMARY. 
427 
published in its Bulletin an account of the sturgeon’s reproduction (sturgeon 
of the Volga), by Professor Owsjannikow. It seems that the sterlet 
( Acipenser ndhmus ), the smallest of the Russian sturgeons, spawns in the 
Volga early in May on rocky bottoms, the temperature of the water being 
at 10° R. ( = 54|° F.). The eggs are readily fecundated by the artificial 
method. After they have been in the water a few minutes they adhere to 
any object which they touch. The development of the embryo can be 
observed in progress at the end of one hour. On the seventh day they 
hatch. At first the young fish are 0 m, 007 (about inch) long. At the 
age of ten weeks they are nearly two inches long. They feed on the larvae 
of insects, taking them from the bottom. Both in the egg and when 
newly hatched, the sterlet has been taken a five days’ journey from the 
Volga to Western Russia, and in 1870 a lot of the eggs was carried to 
England to stock the River Leith. This species passes its whole life in 
fresh water. The other species inhabiting the Baltic, Alcipenser sturio , 
A. Huso , A. stellatus , and A. Giildenstddtii, are anadromous. These species 
hybridise, and freely, and from this circumstance some Russian savants have 
pronounced them only varieties instead of species. 
How should Objectives be Named. — Dr. Ward says that the following are 
some of the more important queries which still remain open. Should the 
standard 1-inch objective be characterised by magnifying ten diameters as 
used in the compound microscope, or should it be compared to a simple 
lens of actually measured focus or foci? Should the objective be named 
by its equivalent focal length, or by it3 amplifying power, or both? Should 
our standard distance of measurement be changed from 10 inches (254 milli- 
metres) to 9f inches (250 millimetres) ? From what point in the objec- 
tive shall the distance to the scale be measured ? At what point of screw- 
collar adjustment shall the objective be placed for rating its angular 
aperture and amplifying power ? Should the name ocular be substituted 
for “ eye-piece” in general use? — Monthly Microscopical Journal (July). 
Various Microscopical Tapers. — The following are some of the papers 
published in the “Monthly Microscopical Journal” for the past three 
months, July, August, September: — “Micro-Pantograph.” By Isaac 
Roberts, F.G.S. “ On Bog Mosses.” By R. Braithwaite, M.D., F.L.S. 
“ Remarks on the Homological Position of the Members constituting the 
Thecated Section of the Class Rotatoria.” By Charles Cubitt, F.R.M.S. 
“Further Remarks on Tolies’ |th, and Powell and Lealand’s Immersion 
Ygth.” By Edwin Bicknell, Cambridge, Mass. “ On Uniformity of Nomencla- 
ture in regard to Microscopical Objectives and Oculars.” By. R. II. Ward, 
M.D. “ Notes on some Microscopic Organisms.” By Prof. A. M. Edwards, 
U.S.A. “Notes on Victoria Mollusca and their Palates.” By Charles 
M. Maplestone. “ The Nerves of Capillary Vessels and their probable 
Action in Health and Disease.” By Dr. Lionel S. Beale, F.R.S., Fellow of 
the Royal College of Physicians, Physician to King’s College Hospital. 
“Remarks on the Nomenclature of Achromatic Objectives for the Compound 
Microscope.” By Dr. J. J. Woodward, U.S. Army. “ Our Present 
Medical and Students’ Microscopes.” By R. H. Ward, M.D. “On 
Euchlanis Triquetra and E. Dilatata.” By C. Hudson, LL.D. “ On 
some Methods for Preparing the Tissues of the Frog Tadpole’s Tail.” 
