52 PEOaBESS OF MICROSCOPICAL SCIENCE. ['^oufmvfinS^^^^^^ 
rod-cells have a distended middle portion, and contain a nucleus. The 
neck of such cells is elongated, and the free margin is furnished with 
a projecting hair or filament. Between the rod-cells are the dentate 
cells. Hesse has succeeded in tracing the termination of isolated 
nerve fibres, and describes them as ending in the rod-cells. On the 
epithelium of the papilla acustica rests a membrane, "membrana 
tectoria," first described by Deiter, which receives in its substance the 
hairs of the filaments of the rod-cells. Corti's cells were everywhere 
absent, but Hesse does not locate the perception of sound exclusively 
in Corti's fibres, but assigns it also to the vibrations of the membrana 
tectoria, and the secondary vibrations of the filaments of the rod-cells. 
Comparing the ear of the frog with that of the higher animals, the 
author says : — " Ampullee and semicircular canals are here as much 
difterentiated as in the higher animals, but all the remaining parts, 
with the exception of the lagena, do not rise above the level of the 
auditory vesicle." "Yet all parts are present; those most essential 
have remained the same, only those which are inessential are variously 
modified, as is likewise the method of their arrangement." The author 
is anxious to extend his investigations to fishes and the higher 
animals, to make the chain of observations complete, " and in order, 
if possible, to find the general principle in the structure of the 
auditory apparatus here verified, namely, the attachment of an 
isolated nerve fibre to an isolated cell provided with a vibrating 
hair, which terminates either in a vibrating membrane, or rises free 
into the endolymph." 
Tlie Anatomy of the Genus Gordius. — Dr. H. Grenacher, Wiirzburg, 
has made investigations on this animal by means of transverse 
sections with a razor. Tropical animals were chosen for examination. 
The external layer of the cuticle contains papillie, some of them 
provided with threadlike processes of considerable length. The 
papillae are coloured ; canals exist in the epidermis. The ven- 
triculus extends as a cylindrical canal from before backwards. The 
author considers it the homologue of the abdominal line of the 
nematodes ; it divides behind ; its functions are unknown. Beneath 
the epidermis is a muscular stratum; its fibres do not anastomose. 
The intestine is surrounded by the perienteric cellular tissue, consist- 
ing of beautifully arranged pentagonal or hexagonal cells, resembling 
vegetable cellular tissue. The intestinal canal and the several organs 
are inseparably united. The sexual organs are fully developed, even 
in the parasitical state of the animal. The intestinal canal has no 
independent termination, but enters into the uterus. The uterus 
divides towards the front into two lateral oviducts and a central 
receptaculum seminis. Higher up appear the ovaries. Subsequently 
the intestine changes its place, lying not superiorly but inferiorly to 
the receptaculum seminis. Advancing still higher up, the receptaculum 
seminis disappears, and the ovaries occupy nearly the whole of the 
internal parts, and the intestine becomes triangular. In the male the 
cloaca lies in the immediate neighbourhood of the place where the 
body bifurcates, and receives the vasa differentia and the intestine. 
A mouth has been discovered, but its connection with the intestine 
