se 
A fine silk thread may be tied around each egg during the two- 
cell-stage (or later) so that the egg is compressed into a dumb- 
bell shaped figure. Such eggs produce normal embryos even when 
the tightened thread passes between the two blastomeres. A single 
embryo results. 
In a few cases a fine needle was thrust through the membrane 
above the blastoderm and moved along, as far as was possible, between 
the first two blastomeres. A whitish plate of dead protoplasm remains 
in some cases when the needle is removed. These eggs develop a 
single perfect embryo. Perhaps this was to be anticipated as the 
periblast still unites at the periphery the two blastomeres. 
Concrescence. 
We may now examine the experiments that bear on the problem 
of concrescence of the fish-embryo. Two points are to be tested: first, 
is the head a fixed point, second, does the substance of the germ-ring 
go to make up the embryo? I must express my obligations to Prof. 
WHITMAN for suggestion and criticism of this part of the work. 
If we take an embryo at the time when the first trace of the 
germ-ring makes its appearance and with a fine needle stick ex- 
actly in the center of the blastoderm, so that the germ-ring lies at 
all points equally distant from the point of puncture, we shall find, 
that as the embryo appears at one point of the germ-ring its anterior 
ends extends exactly as far as the point of injury. Whether this tri- 
angular accumulation of material with its apex at the point of injury 
forms in situ or whether the lateral and medium portions of the germ- 
ring pass forward to this point I am not prepared to say. Careful 
sections will I hope settle this point. It is certain that quite a con- 
siderable portion of the early germ-ring takes part in the thickening 
forming the base of the triangular mass and I think it can be shown 
that to a certain extent the material lying immediately to the right 
or left passes in towards the medium line as the embryo begins to 
elongate. After the head end has reached the point noted above it 
does not progress any further forward for if the point of injury had 
been a little excentric i. e. more toward the side in front of the em- 
bryo, the head end never extends to it, but falling short of the small 
“extraovate” retains a constant relation to it during the later stages. 
Prof. Warrman has, from a study of the normal embryo, also 
reached the conclusion that the head end of the embryo advances (or 
is formed) at the apex of the early blastoderm. Although his account 
is not as yet published he has described the process in his lectures. 
