138 Transplantation of the Lips of the Blastopore 
The following experiments were made, partly with the view of deter- 
mining what organ-forming stuffs are present in the lips of the blasto- 
pore; but more especially to determine the extent of independent self- 
differentiation possessed by this structure when small pieces were isolated 
and transferred into strange environments. In the examples of asyn- 
taxia medullaris there develops from the lips of the blastopore on either 
side a half embryo with spinal cord, notochord, and myotomes, so that 
evidently the fusion of the lips is not necessary for their differentiation, 
but it might be, of course, that some of the other relations are essential, 
such as the anterior, posterior, or the lateral connections with the embryo. 
But by cutting out and transplanting small sections of the lips these 
factors were eliminated. 
The first series of experiments were made on rana palustris at a time 
when the dorsal and lateral lips are well marked, the ventral lip is just 
beginning to appear. Small blocks of tissue were cut from the dorsal 
and lateral lips (1, 2, 3, and 4, Fig. 1), so as to include the entire thick- 
ness of the lip with both ectoderm and endoderm. These pieces were 
transplanted beneath the ectoderm of older embryos of the same species 
in the region of the otic vesicle: The embryos into which they were 
transplanted show the beginnings of the tail bud. The pieces trans- 
planted are soft and delicate, and of course very liable to injury during 
the operation by distortion, tearing, or loss of a portion. 
In the first experiment (ta,), piece (1), Fig. 1, was transplanted into 
an older embryo which was killed 7 days after the operation. The sec- 
tions (Fig. 2) show in the region of the otic vesicle a large notochord, 
perfectly normal in its differentiation and extending for many sections 
in a direction parallel to the long axis of the central nervous system. 
Portions of the chorda are irregular in outline and it is not quite as large 
as the normal one in cross diameter. Near the chorda and ventral to 
the otic vesicle is a large mass of muscle, irregularly arranged, normal 
in its differentiation, showing striation and other characters of myo- 
tomic muscles. I am unable to find any nerves going to this muscle 
mass and it lies in a position where normally there is no muscle. 
Ventral to the notochord and medial to the muscle mass is a piece of 
central nervous system having both white and gray substance and a 
central canal. In places the nerve cells seem to be degenerating. The 
central canal is closed at either end. 
I am unable to determine if any of the transplanted tissue differen- 
tiated into endoderm, though some degenerating cells in this region may 
