ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
361 
remaining, as Duval lias sliown, normal through the gestation. (4) In 
Insectivores the destruction of the mucosa is almost complete during 
gestation, and the reaction varies with the genera, being sometimes 
mostly epithelial, sometimes mostly dermic. (5) In Rodents there is 
a rapid disappearance of the glands (after a short phase of hypertrophy 
in the rabbit), and the modifications of the dermis are most prominent. 
Here again the destruction extends into the deep dermic layers (Duval). 
(6) In bats ( Vespertilio murinus), the hypertrophy affects the dermis, 
and the necrosis penetrates through the whole thickness of the dermis, 
except to some elements intimately applied to the musculature. (7) In 
the bat there is a complication. A limited portion of the dermis, 
in immediate contact with the external placental* surface, differentiates 
from the deep layers, and undergoes independent modification. It 
forms a vascularised para-placentar layer. (8) When there is a not- 
able difference between the volume of the fertilised ovum and the 
uterine cavity, and when the swelling of the mucosa is strongly marked, 
the ovum is surrounded in a reflected decidua. 
Cell-Bridges in TJnstriped Muscles.* — Dr. H. Triepel notes that 
many investigators have described intercellular bridges in the unstriped 
muscle of Mammals. He has added to the list of cases by finding them 
very distinctly in the longitudinal intestinal musculature of the ox. He 
fixed his material in 4 per cent, formol solution, and stained with haema- 
toxylin and neutral orcein. The appearance of bridges is not due to 
longitudinal ridges, for there are none ; but a longitudinal striation 
nr fibrillation does occur in the cells. He observed spiral ridges with 
two or three turns on a cell, but these are contraction phenomena. The 
intercellular bridges are not to be confused with marginal irregularities 
which ^correspond to the spiral ridges, nor with certain long threads, 
which are probably due to insinuated connective tissue elements. 
Comparative Histology of the Liver.f — Herr J. F. Holm has 
compared Myxine , Ammocoetes , Petromyzon, and Scyllium , as regards 
the structure of the liver. As long as the liver is directly secretory, 
it has the character of a tubular gland, as is plainly seen in Myxine. 
In the larval lamprey the same condition occurs, but it is lost as the 
secretory function ceases. In the dog-fish there does not seem at first 
sight much ;hint of a glandular character, but this comes out when 
embryonic stages are observed. The primitive state of the liver was 
doubtless that of a tubular gland. 
Permeability of the Skin.i — Margherita Traube-Mengarini has 
experimented on the osmotic permeability of the skin. There can be 
but little, else fresh-water animals would swell up and marine animals 
would shrink. Only in parasites which live in a solution of constant 
esmotic pressure is the skin markedly permeable. Thus a living 
Opalina may be readily penetrated by eosin, if the medium is other- 
wise suitable. In Metazoa, the intestinal tract alone shows osmosis. 
Thus, if frogs swallow the coloured water in which they are placed, 
they are gradually coloured through and through ; but if the mouth 
* Anat. Anzeig., xiii. (1897) pp. 501-3. 
t Zool. Jahrb. (Abth. Anat.), x. (1897) pp. 277-86 (2 pis.). 
% Rend. Acc. Lincei, v. (1S96). See Biol. Centralbl., xvii. (1897) pp. 29-30. 
