PLATE 2 
EXPLANATION OF FIGURES 
All figures except figs. 12 and 15 were drawn from camera lucida sketches of 
living specimens of embryonic tissue isolated in clotted lymph. 
7-11 Five views of the same group of nerve fibers made at different times (ex- 
periment Is, 137), medullary cord tissue from R. palustris, 3.3 mm. long, lymph 
from R. pipiens (the interval between the first and last figure represents 34 hours). 
X 350. 
7 Apparently single fiber (n/) growing out from a pointed cell (cti) which pro- 
jects from a mass of cells (ms) one day after isolation of tissue. April 28, 1908, 
12.25 p.m. 
8 Same fiber, 2 p.m. Fiber is now clearly double. 
9 Same group of fibers. 10.25 p.m. Four distinct fibers (n/i-n/4) are now vis- 
ible. The fibrin filaments (thr) shown in this figure were present in the earlier 
stages but were omitted from the original sketches. 
10 Same group. April 29, 11 a.m. n/5 possibly a branch of n/ . 
11 Same group. 10.30 p.m. Continuation of n/i and upper branch of n/2, 
unfortunately left out of sketch. Note migration of cell (ct2). Identity of other 
isolated cells in figs. 10 and 11 is uncertain. 
12 Three cells from a specimen preserved five days after isolation. Osmic 
vapor followed by Tellyesniczky's fluid, stained in O. Schultze's haematoxylin. 
The cells have much branched processes which end indefinitely in the coagulum 
which pervades whole specimen. Many isolated cells of this kind are in the speci- 
men, which is quite typical. Experiment Is, 157, medullary cord from R. palus- 
tris embryo; R. clamitans lymph. X 350. 
13 Row of ectoderm cells from the abdominal region, showing fringe of amoe- 
boid hyaline protoplasm {pl.fr. ). Experiment Is, 75, two days after isolation. 
Tissue from palustris embryo in palustris lymph. X 350. 
14 Similar specimen. In this case the ectoderm cells, which are taken from the 
branchial region, show the cuticular seam (cut). The hyaline fringe (pl.fr.) be- 
longs to cells lying below the main row. Experiment Is, 87, one day after isola- 
tion. Tissue from palustris embryo in palustris lymph. X 350. 
15 Three cells from the medullary cord of frog embryos about 3.3 mm. long, 
in which the medullary folds had closed and the tail bud was just beginning to 
appear, prepared from the living specimens; a and b taken from an embryo of R. 
sylvatica, dissected and examined in 0.2 per cent NaCl; c taken from an embryo 
of R. palustris, examined in tap water. The latter cell (c) has imbibed water 
and the cell membrane is very distinct at one side. Nucleus shows as a clear space 
in each cell. X 350. 
16 Whole piece of tissue (medullary cord, with small portions of muscle plates 
attached) isolated in lymph, two days after preparation. The dark area repre- 
sents a thick opaque mass of tissue. Thin sheets of cells (I) and isolated cells are 
shown on all sides, nf, nerve fibers projecting out into lymph from under the 
masses of cells, fil, threads of hyaline protoplasm bridging spaces between masses 
of cells, cd, band of cells in single file. Experiment Is, 124. Tissue from pipiens 
embryo, lymph undetermined. X 32. 
