SCIENTIFIC SUMMARY. 
291 
Amoeba Blattee. — Prof. Leidy brought under the notice of the Academy 
of Natural Sciences of Philadelphia the occurrence in the interior of the cock- 
roach of an amoebiform parasite described by Prof. Biitschli under the name 
of Amoeba Blattee. He found it abundantly associated with two other 
Protozoans and two parasitic worms of the genus Oxyuris. Prof. Leidy 
thought that this amoeboid parasite differed sufficiently from Amoeba to be 
placed in a distinct genus, which he names Endamceba in allusion to its 
occurrence as an internal parasite ; it differs from Amoeba in the absence of a 
contractile vesicle, and commonly also of vacuoles, and in the want of 
differentiation of endosare and ectosare ; and from Brotamceba in the 
possession of a well-defined nucleus. Prof. Leidy adds : — 1 Endamceba 
Blattee affords a good example of a primitive, active nucleated organic 
corpuscle , or a so-called organic cell without a cell-wall. In the encysted con- 
dition it would be a complete nucleated organic cell. Endamceba may be 
recommended as a convenient illustration of a primitive form of the organic 
cell on account of its comparatively ready access.’ He gives as the size of 
globular forms, 0-054 — 0-075 millim. in diameter and of elongated forms 
0-075 by 00*6 millim. to 0‘15 by 0‘09 millim. — ( Proc . Acad. Nat. Sci. Philad., 
October 7, 1879.) 
A Freshwater Medusa. — A fortnight ago zoologists were startled by a 
report that a small Medusa had been found living in great abundance in a 
tank containing fresh water in the Botanic Gardens in the Regent’s Park. 
The tank was that in which the Victoria regia is grown, and the water in 
it is habitually kept at a temperature of 85-90° F. The case was par- 
ticularly remarkable, for no known example of a Medusoid organism living in 
fresh water was previously known — in fact, contact with fresh water is 
generally fatal to such animals — and although they may be found in the 
mouths of rivers, it is always in that part of the tideway where the water is 
quite salt that they are met with. The little Medusa belongs to the so- 
called naked-eyed division of the late Prof. Forbes. The general run of the 
specimens are about the size of half a pea, but some of them are said to 
attain a diameter of about half an inch. They consist of a nearly hemi- 
spherical bell, from the centre of which depends a long stomachal peduncle, 
hanging down some distance below the margin of the bell. The bell or 
umbrella is traversed by four radiating canals, which start from the point of 
insertion of the stomachal peduncle and run to the margin of the bell. From 
these canals the generative organs depend, forming oval sacs between the two 
membranes forming the bell. These sacs contain either ova or spermatozoids, 
so that the animals are unisexual. The aperture of the bell, as in all naked- 
eyed Medusae, is narrowed by a membrane (velum), extending inwards from 
the margin of the bell, which bears a great number of tentacles, four of 
which are considerably larger than the rest, and correspond to the radial 
canals. The other tentacles are much more numerous. In large specimens, 
according to Prof. Lankester, there are seven secondary tentacles in each 
of the spaces between two primary tentacles, while the interspaces between 
the secondary tentacles are occupied by groups of six tertiary tentacles. This 
gives 224 as the total number of tentacles on a fully developed specimen. 
The otoliths are placed along the line of attachment of the velum, and are 
about 80 in number ; the otocysts, according to Prof. Lankester, are produced 
