978 General Notes. [ November, 
New FRESH-WATER CŒLENTERATE.—Dr. Ussow describes 
(Ann. and Mag. Nat. Hist., xvi, p. 110, pl. Iv, 1886) a new 
fresh-water Coelenterate from the rivers of Russia. It is a Hy- 
dromedusa, but differs so from all others that it is made the type 
of a new genus, Polypodium. The young stages are remarkable 
in that they are passed as parasites in the eggs of the sterlet, 
about one-fifth of the eggs being thus infected. This stage is 
described as a cylindrical spiral twisted tube with numerous 
lateral buds. This feeds upon the yolk granules which are taken 
up by the ectodermal cells and are thence passed to the endoder- 
mal ones. From this is developed the free stage, which is more 
like a normal Hydromedusa and is provided with six, twelve or 
twenty-four tentacles, but lacks an umbrella. The perfect or 
sexual stage is not known. A full paper is promised soon. 
Nervous SYSTEM OF THE SEA-URCHIN.—M. H. Pronho states 
that if one suitably treats a portion of the integument which 
covers the test of Achinus acutus with chloride of gold or citric 
acid, numerous bluish lines connected by frequent anastomoses 
will become apparent; the appearance forcibly recalls that figured 
by Professor Loven of the peripheral nervous system of Brissop- 
sis lyrifera. Examined under a power of 500, the plexus will be 
found to consist of a large number of fibrils, and some of the 
principal bundles will be seen passing towards the spines and 
adjacent pedicellariz. The fibrils of which this plexus is formed 
are identical with those of the tentacular and ambulacral nerves, 
and each is continuous with the fiber from the ambulacral nerve 
which emerges from one of the tentacular pores; the plexus lies 
tween the external epithelium and a layer of connective tissue 
which sends off a number of connective bands through the 
meshes of the nervous plexus to support the epithelium. At the 
detect in the plexus, but they are very numerous and easy to see 
in the nerve-ring; the author does not, however, agree with 
Romanes in his description of these elements. M. Pronho has 
also been able to make out a nervous genital ring, which cor 
nects the five genital glands with one another and, by means © 
the five ambulacral trunks, with the peribuccal nervous pentagon. . 
— Comptes Rendus, cii ( 1886), pp. 444-6. 
= Tue Crustacean CARAPAx.—There seems to be a certain fatal- 
= ity connected with some scientific facts. Away back in 1834 vi 
_ late Henri Milne-Edwards had a conception of the true ga gee 
ogy of the crustacean carapax, and eighteen years later James ©. 
_ Dana still further efaborated the matter. But, notwithstanding 
_ the weight of their authority, their views failed to gain Ee 
cceptance and almost every text-book! to-day states that th 
