NOTES AND MEMORANDA. 
81 
tary post-abdomen is reduced to two rounded lobes, each bearing two 
Lairs. The antennae also much more resemble the type of the Cythe- 
ridae than that of Cypridae. 
The reproductive apparatus does not present anything peculiar ; it 
resembles that of the Ostracodes in general. Besides the sexual tube 
there is a receptaculum seminis in the female, and a very complicated 
chitinous copulatory apparatus in the male. The vulvae are placed 
below the two post-abdominal lobes. 
With regard to its mode of life, this crustacean is unable to leave 
the bottom. It does not swim at all ; it sometimes creeps, but usually 
buries itself, and thus travels in the mud and organic debris by the 
aid of its feet and antennae. The hairs and segments of the feet are 
driven into the mud, which serves as a support. The strong hooks of 
the basal articulation are especially useful, but give a somewhat 
awkward appearance to the mode of progression. The mechanism of 
this locomotion may be compared to that of a man who endeavours to 
advance upon his knees, aiding himself with his toes. 
The two pairs of antennaB act in opposite directions ; their action 
may be compared to that of the two anterior paws of a mole. These 
are the members which enable our crustacean to bury itself in the 
mud. 
With reference to the origin of this organism two suppositions may 
be formed : it may be descended from a marine species introduced by 
some means into our lakes ; or it may have for its ancestor a fresh- 
water crustacean ; the genus Candona would be that which it most 
resembles, though nevertheless very dissimilar. The field of hypo- 
theses remains open upon this point.* 
A Microscopic Trap for a Hover. — Mr. F. A. Bedwell describes in 
the ‘ Midland Naturalist ’ a very useful contrivance to keep rotifers 
and other lively things within the field of view. A friend had sent 
him some specimens of Hydatina senta which he was anxious to ex- 
amine with a high power. He says “I first tried my usual cell, a 
ring of microscopic glass, the very thinnest I can get (and answering 
to the No. 6 on the adjustment collar of the i), with a piece of glass 
as thin as itself over it. This prevented the whirligig performance, 
but rest was out of the question, and following even Hydatina’s charms 
under a gets monotonous when you are always only just catching her 
up. So I tried an old idea in a new form. I took a flat glass slide 
and dropped two Hydatinas on it, with a small drop of water about 
half an inch in diameter. Upon this drop I laid some cotton wool, 
frayed out so as to be much diffused in space. I then put the thin 
sheet of glass on that, gave the sheet a touch with a needle to set the 
capillary attraction up, and Hydatina’s gambols were over. I used an 
to examine her easily.” 
High-angled Objectives for Histological Worh. — In his address to 
the Dunkirk (U.S.) Microscopical Society, Professor J. Edwards Smith 
strongly advocates for histological investigations objectives of very 
* ‘ Bibl. Uiiiv.,’ Oct. 15, 1877. ‘ Arch, dua 8ci.,’ p. 331. ‘Ann. Nat. Hiatorv,’ 
Feb. 1878. 
