"^JoiSJjanSyTS PKOQRESS OF MIOROSOOPIOAL SCIENCE. 51 
pbject-table. Tlie temperature of the preparation, however, did not 
always correspond with that of the table, but was liable to con- 
siderable fluctuation through the influence of the objective, for 
"the temperature of the preparation must depend essentially on the 
objective, and, as the latter is only a part of the great mass of metal 
in the microscope, of course on the temperature of the whole 
microscope." To correct this to some extent, Engelmann inserted an 
ivory tube, 30 Mm. long, between the objective and the tube of the 
microscope. The ivory tube being a bad conductor, the graver errors 
are avoided. — Ihid. 
Observations on Krause's Memhrana fenestrata of the Betina, by V. 
Hensen. — This short paper has chiefly reference to a dispute between 
Krause and Hensen about Eitter's filaments on the rods of the retina, 
the existence of which the former denies, accounting for them by an 
optical illusion and want of care in using chemical re-agents. — Ihid. 
On Noctiluca miliaris, by Victor Cams, is a reply to some 
remarks made by Dr. Doenitz on V. Carus's observations on Noct. mil., 
anent the parenchyma of its body. Carus has described a gelatinous 
framework with parenchymatous filaments, ending in meshes beneath 
the skin, united to the latter by a layer of cells. Dr. Doenitz suspects, 
that Carus has mistaken sea-water for an organic substance. — Ibid. 
The Organ of Hearing in Frogs. — Dr. C. Hesse, of Wiirzburg, has 
a paper on this subject in Siebold and KoUiker's * Zeitschrift fiir 
wissenschaftliche Zoologie,' Part III. Considerable difficulties must 
have attended the examination of so ill-defined and minute an organ 
as the auditory apparatus of the frog, especially as, on account 
of the cartilaginous encasement of the internal ear, it cannot be 
lifted out of its connection entirely without being destroyed. Only 
two entrances into the inner ear were discovered, one for the 
auditory nerve, and the other the foramen ovale ; no foramen 
rotundum was present. The cartilaginous walls contain fusiform 
cells. The anatomy of the semicircular canals and the ampuUee 
in the frog is neaily the same as in man, but instead of the 
vestibule and cochlea, only a rudimentary vesicular structure is 
seen, the auditory vesicle. Yet even in this simple structure the 
rudiments of all those parts may be observed that enter in man and 
the higher vertebrate animals into the constitution of the vestibule and 
cochlea. Hesse has carefully traced all of them, and established an 
analogy between these rudimentary parts and the corresponding 
structures in the ear of man. The first division of the auditory 
vesicle of the frog is effected by a perpendicular partition into the 
pars vestibularis and pars cochlearis, the former communicating with 
the semicircular canals and the ampullae. The p. vestibularis or 
utriculus communicates also with the p. cochlearis by means of the 
apertura utriculi, a sjjot where the partitional division between these 
two cavities is incomplete. The walls of these compartments are 
lined partly with pavement epithelium, and partly with cylindrical 
dentate cells and rod-cells. It is the latter, that are of special im- 
portance, as constituents of the organ of hearing. They are confined 
to special parts, such as the macula and the papilla acustica. The 
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