Warren Harmon Lewis 139 
possibly be endoderm. It is evident from this experiment that tissue 
from the dorsal lip of the blastopore possesses great power of self-differ- 
entiation, is already predetermined, and does not need the usual normal 
relations with the rest of the embryo for its differentiation. At how early 
a period these tissues are capable of independent self-differentiation is, 
of course, only possible to determine by further experiments along per- 
haps somewhat similar lines of transplantation. 
The transplanted piece in another similar experiment (ta,) of this 
series, taken from the region (2) (see Fig. 1), differentiated into noto- 
chord, striated muscle, and nervous tissue. The latter, however, is only 
imperfectly differentiated and shows many degenerating cells. This 
embryo was killed 7 days after the operation. 
In another experiment of the same series (ta,), piece (3) (see Fig. 
1), was transplanted and the embryo killed after 7 days. here differ- 
entiated from it a large mass of striated muscle without nervous con- 
nection and a small piece of the neural tube consisting of a single layer 
of cells (see Fig. 3). No traces of notochord were found so it seems 
probable that the cells of the transplanted piece destined to form chorda 
were lost during the operation. The more lateral position of piece (3) 
does not explain its absence as from piece (4) (see Fig. 1, experiment 
ta,), a large normal appearing notochord and neural tube tissue differ- 
entiated, the latter contains many degenerating cells. No muscle tissue 
was found and its rudiment was probably lost in transplantation. Both 
‘of the above embryos were killed 7 days after the operation. 
In another series (tb) four pieces from the dorsal lip of the blastopore 
of a gastrula, the same age as in the preceding series, were transplanted 
into the otic region of similar older embryos, with beginning tail buds. 
These embryos were killed 6 days after the operation. As in the preced- 
ing series muscle and chorda develop into quite normal tissue, the former 
without any nervous connection. The neural tube is always present but 
shows more or less extensive degenerative changes. 
In one of these experiments (tb,) the chorda is in contact with the 
ectoderm, the latter shows here a modification of its staining reaction with 
hematoxylin and Congo red. Here, also, the cells of the inner layer of 
the ectoderm are elongated in an axis perpendicular to the surface. These 
modifications were very likely brought about in some way through the 
contact influence of the notochord. 
In another similar series (te) an embryo (te,) was killed 9 days 
after the operation. ‘The sections show ventro-lateral to the otic vesicle 
