568 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
tuberance becomes turbid. It is not necessary to assume an autonomic 
mobility of the hyaline substance in order to explain the origin of the 
hyaline protuberances; they are due to a relaxation of the limiting 
layer and the morphoplasmic framework. 
During nuclear and cell-division the distribution of the hyaline 
substance and framework substance changes in very regular fashion. 
The limiting framework is loosened out, and the accumulation of a 
hyaline area traversed by a loose framework precedes the new nuclear 
formation. 
The facts observed are in no way inconsistent with Engelmann’s 
hypothesis that contraction-processes imply coagulation-processes. 
Unfertilised trout ova may be kept alive for four weeks in running 
water, but some interesting changes occur. 
In ova of rainbow-trout which had remained seventeen days unfer- 
tilised, His observed numerous small astrospheres with multipartite 
microcentra. No nuclei or chromosomes were any longer recognisable. 
The appearance of astrospheres and centrosomes independently of the 
sperm suggests the original presence of autonomic ovum-centra. No 
cells are formed, but a sort of syncytium — with degenerate chromosome 
development. 
Nucleolus of Hedgehog Ovum.* — Dr. E. Wace Carlier describes 
the various phases of the nucleolus in the ovarian ovum of the hedge- 
hog. When the nucleus seems to have attained its maximum size, the 
nucleolus may be bodily extruded into the cytoplasm, where it breaks 
down ; but more frequently it is retained in the nucleus and undergoes 
vacuolation. He sides with those who regard the nucleolus as consist- 
ing almost entirely of effete material resulting from the cellular meta- 
bolism. 
Amniotic Fluid, f — Dr. Y. Kistiakowski adduces numerous facts 
which lead him to conclude that the amniotic fluid in the cow originates 
during the first period of the development of the foetus by transudation 
from the blood-vessels of the placenta, and that in the second half of 
the developmental period it is formed from the excretory activity of the 
digestive organs of the foetus. 
Development of Vertebral Column of Reptiles.:]: — Herr H. Manner 
has followed this from the origin of the sclerotome to the differentiation 
of the vertebrae in Lacerta agilis, Anguis fragilis , Coronella laevis , and 
Tropidonotus natrix. From the first the sclerotomes are sharply defined 
by the boundary of the primitive segment and by the vessels which lie 
between the protovertebrae. The intervertebral cleft extends at first 
onJy into the middle of the sclerotome, and the densest accumulation 
of cells is found in the lateral third. 
In the second stage the intervertebral cleft extends from the muscle- 
plate to the perichordal layer, and divides the sclerotome into two equal 
portions. 
A third stage is characterised by the intrusion of the muscle along 
the intervertebral cleft, and the modifications consequent on this. 
* Proc. Scot. Micr. Soc., ii. No. iii. (1897-8) pp. 184-8. 
t Physiol. Russe, i. (1899) pp. 155-66. 
X Zeitschr. f. wiss. Zool., lxvi. (1899) pp. 43-68 (4 pis.). 
