606 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Formation of Germinal Layers of Amphioxus.* — Mr. E. W. M‘Bride 
lias lately undertaken a reinvestigation of the whole subject of the develop- 
ment of the lancelet, and hopes to shortly publish his completed results. 
He points out that the development of Amphioxus is exceedingly important 
from a theoretical point of view, since in it we meet with the only 
instance of an unmodified Vertebrate egg, in which the yolk is small in 
quantity and evenly distributed, so that the early development processes 
are not impeded by its presence. As Mr. M c Bride points out, it is 
necessary to interpret the development of other Vertebrates in terms of 
the development of Amphioxus , and not vice versa. 
From the facts here briefly related, it is clear that the coelom of 
Amphioxus is an undoubted enterocoele, and that the formation of the 
mesoblast in this animal is easily referable to the type which Bateson 
has described in the case of Balanoglossus. The head-cavities represent 
the proboscis-cavity, the first myomeres the collar-cavities, and the great 
posterior mesoblastic pouch, which becomes segmented into somites, the 
trunk-cavity. 
f3. Histolog-y. 
Physiological Significance of Direct Cell-Division.f — MM. E. 
Balbiani and F. Henneguy remind the reader that histologists are not 
agreed as to the physiological significance of direct cell-division or 
amitosis. Some look upon it as a phenomenon of degeneration, and state 
that the daughter-cells rarely, if ever, divide again ; others think that, 
in addition to the degenerative division, there is a regenerative one, in 
consequence of which the cells are able to continue to multiply. Our 
authors, from experiments made with tadpoles, are inclined to take the 
second view. They state that, if in a damp atmosphere one keeps in 
contact the ends of the tails of two tadpoles, at the end of an hour or 
an hour and a half the fragments are sufficiently attached to one another 
not to be separated when placed in water. The fusion is quite super- 
ficial, and is effected by epithelial cells which proliferate very rapidly. 
There are produced epithelial buds which are formed by a series of 
successive and rapid amitoses. From the observations of many histolo- 
gists it is clear that a mitosis takes at least three hours, whereas in the 
authors’ observations a large number of cellular divisions occurred 
within the space of one hour. It is clear that the amitosis which occurs 
in the tadpole is not a degenerative but a regenerative process. 
Basic Substances of the Nucleus.;}; — Prof. A. Kossel has shown that 
the nuclein substances in the nuclei of animal cells frequently occur in 
salt-like union with basic substances which have a more or less marked 
proteid-like character. Such a basic substance is the histon which 
Kossel found in the nuclei of the red blood-corpuscles of birds, or the 
protamin which Miescher obtained from the spermatozoa of the salmon. 
Kossel estimates the formula of protamin-sulphate as C 16 H 31 N 9 0 31 , 
h 2 so 4 . 
He has studied in particular the sperm-material of the sturgeon, and 
has found a substance, sturin, closely resembling protamin, with the 
* Proc. Camb. Phil. Soc., ix. (1896) pp. 150-3. 
f Comptes Rendus, cxxiii. (1896) pp. 269-70. 
X SB. K. Preuss. Akad., 1896, pp. 403-8. 
