576 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
I, Histology. 
Researches on Structure.* * * § — Prof. O. Biitschli in this volume de- 
scribes his observations on the structure of piotoplasm, of gelatin and 
similar colloids, and of starch-grains and crystalloids. His object is 
to show that in all these the minute structure is essentially similar — is 
the foam-structure so closely associated with his name. In many of the 
structures this is not directly apparent, but as the author believes can be 
manifested by the use of reagents. In many cases, and notably in the 
case of cell-walls and starch-grains, the results obtained are in striking 
variance with those of other observers on the same subjects. 
Intestinal Epithelium.f — Herr 1V1. Heidenhain contributes one of 
his careful histological studies, dealing in the present instance with the 
structure of the cells in intestinal epithelium. He shows that in the 
frog the plasmic fibres form very regular systems, the limits of which 
are often straight lines, and the symmetry of which is definitely bilateral. 
In short, he describes a marvellous architecture, the complexities of 
which far outrun the present possibilities of physiological interpreta- 
tion. 
Direct and Indirect Division. :£ — Herr W. Rudnew has been led by 
his studies on the early development of a species of Coregonus to the 
conclusions: — (1) that direct division is a palingenetic phenomenon 
which in the genesis of the cell has preceded, as it may still precede, the 
occurrence of indirect division ; and (2) that amitosis is often a quite 
normal phenomenon which may be followed by mitosis without any 
detriment to the organism. 
Luminous Organs in Spinax niger.§ — HerrL. Johann describes the 
minute structure of peculiar epithelial organs which are seen as brown 
or black spots on the skin of this fish. Each consists of 2-5 layers 
of 4-6 cells arranged in a circle, and the elements may be distinguished 
as luminous cells and lens cells. There is no special innervation apart 
from that of the skin as a whole. The primordium resembles that of a 
skin-gland. The luminosity was observed by Dr. Th. Beer. 
Intestinal Secretion and Absorption. || — Dr. W. Moller has studied 
this in numerous mammalian types. In all the forms investigated, 
except pig (?), dog, and cat, the Lieberkiihn-crypts in the small intestine 
contain typical glandular cells. In these the secretion appears in the 
form of granules, — at first small and stainable, but gradually increasing 
in size and losing their stainable character. Finally, as in salivary 
glands and pancreas, the secretion is expelled in the form of drops into 
the lumina of the glands. 
These glandular cells are quite distinct from the mucus-secreting 
cells. The latter are also well marked off from the adjacent epithelial 
cells. 
From his investigation of the sheep’s intestine the author concludes 
* ‘ Untersuchungen iiber Structuren,’ Leipzig, 1898, viii. and 410 pp., 99 figs., 
and Atlas of 27 plates. See Bot. Ztg., lvii. (1899) pp. 260-1. 
t Arch. Mikr. Anat., liv. (1899) pp. 184-224 (2 pis.). 
% Physiol. Russe, i. (1899) pp. 129-44 (16 figs.). 
§ Zeitschr. f. wiss. Zool., lxvi. (1899) pp. 136-60 (2 pis. and 1 fig.). 
|| Tom. cit., pp. 69-135 (2 pis.). 
