140 Transplantation of the Lips of the Blastopore 
a well-formed chorda, a group of striated muscle fibers which seem to be 
spreading out in the form of a muscle (m, m, Fig. 5), and a small and 
imperfect neural tube. The other experiments in this series show that 
the dorsal lip has differentiated into chorda, muscle, and nervous system, 
but all three tissues are not always present, however, owing to loss, 
probably in transplantation, of their rudiments. The mutual relation 
of these three tissues varies in such a manner that there is evidently no 
interdependence, as regards differentiation. The muscle develops per- 
fectly normally without any nervous connection for 9 days at least after 
the transplantation, as in none of the experiments can nerves be traced 
to the muscles, either from the host or the transplanted nervous tissue. 
These tissues do not seem to influence the configuration or arrangement 
of the connective tissue about them in any especial manner nor with the 
exception of the one instance where the chorda has modified the ectoderm 
do they influence other tissues in the region in which they are develop- 
ing. In one instance (te,) the chorda rudiment was evidently trans- 
planted near the normal chorda and has differentiated into a chorda, 
lying parallel to the normal one, both are encased in cartilage of this 
region, and in some places there seems to be a slight excess of cartilage 
about the abnormally placed chorda. 
It is possible that by the transplantation of small pieces or even groups 
of cells from younger and younger embryos that the localization of the 
primary organ or tissue-forming substances can be traced back, step by 
step, to their more primitive locations in the egg. It may be possible, 
also, to determine in these early stages correlations necessary for the 
formation of secondary tissues or for the differentiation of these. 
In almost all of these experiments the tissues which have developed 
from the transplanted piece are much greater in bulk, very much greater 
in the case of the chorda and muscle than such a piece would have pro- 
duced in the same time had it remained in the normal position in the 
embryo from which it was taken. This is an indication of how the 
neighboring parts in a normal embryo must interact upon each other, 
regulating the size or extent of growth for each such part. It is possible 
that when such pieces are freed from this influence of the whole on the 
part, that cell division can take place more rapidly and so produce a 
larger piece from the same number of cells than under normal conditions. 
Although at this early gastrula stage the dorsal and lateral lips of the 
blastopore are already determined as regards there subsequent differen- 
tiation to give rise to chorda, muscle, and nervous tissue, there is evi- 
dently considerable difference in the power of self-differentiation in that 
