OUTGROWTH OF THE NERVE FIBER 
825 
of the amoeboid activity of cells, as wa s first pointed out by 
Peters ('85, '89) in the cornea of the frog, and the observations 
of Barfurth ('91) and Born ('96-97) on the epidermis of amphib- 
ian larvae and embryos confirm this view. More recently Eycle- 
shymer ('07) has observed directly the movement of epidermal 
cells over a denuded wound surface in Necturus embryos. 
The phenomena of movement, which may be observed in the 
embryonic cells isolated in lymph, must, in view of the above con- 
siderations, be considered as manifestations of activity similar 
in kind to those shown by cells within the normal embryo. 
The differences which may exist are unimportant for our present 
purpose. For instance, the peculiarities of form (fig. 6) assumed 
by the larger masses of cells when transplanted, are not to be taken 
as an index of a marked abnormality of conditions which might 
introduce entirely new features into the movements of individual 
cells, for these strange formations may be accounted for by the 
peculiar mechanical conditions obtaining in the clot. Analogous 
deviations from the normal in the gross form of parts are found, 
accompanied, however, by normal differentiation of tissues, when 
pieces of the medullary cord are transplanted to strange regions 
within the body of the embryo. 
The phenomena of differentiation permit the drawing of a much 
closer parallel between the behavior of the tissues in their normal 
environment and when isolated in lymph than do the motor activ- 
ities. Each type of cell follows the same course of differentiation 
which it would have taken had it not been removed from the em- 
bryo, as is seen, for instance, in the formation of striated fibril- 
lae in cells from the axial mesoderm, a cuticular border in cells 
from the epidermis, and typical chromatophores from the walls 
of the medullary tube. Ciliary activity, which may persist for 
days in the case of tissue from the medullar}/ cord or the ectoderm, 
and muscle contractions, which occur in the muscle plates when 
transplanted along with parts of the central nervous system, 
bear witness to the possibility of normal functioning under the 
conditions of the experiments. 
It is seen from the above that the behavior of embryonic cells 
when transplanted to lymph is specific as regards the character 
