486 A. W. BELLAMY 
In m/7 LiCl development comes to a standstill within about six 
hours after the eggs are exposed to the solution, although they are not 
killed outright, as shown by the fact that even after twenty-one hours’ 
exposure development proceeds somewhat further when the eggs are 
returned to water. In m/8.5 LiCl eggs, when placed in the solution 
before segmentation begins, do not develop much beyond late cleavage 
stages unless returned to water, when they go ahead to form equatorial 
gastrulae. 
Of the differentially inhibited forms produced in m/10.62 LiCl, 
those of especial interest here are the ones seen after forty eight hours’ 
exposure to the solution plus twenty hours in water; forty-eight hours 
in LiCl plus forty-eight hours in water, and those exposed seventy-six 
hours to LiCl then removed to water for twenty hours or more. Fig- 
ures 39 to 46; 7 to 9, will show more clearly than any amount of de- 
scription the differential nature of the inhibition suffered under this 
treatment. Figures 39, 40 illustrate two embryos after forty-eight 
hours’ exposure to m/10.62 LiCl plus the subsequent twenty-eight 
hours in water. Figure 39 represents a dorsal view showing a perma- 
nent yolk plug, shifted somewhat asymmetrically toward the right; 
small head region, with the neural groove still open anteriorly. Figure 
AO is a lateral view of another embryo from the same lot as the above. 
Figures 41, 42 represent two embryos from the same lot as the above 
after seventy-three hours in water following a previous exposure of 
forty-eight hours to m/10.62 LiCl. The embryo 41 presents a perma- 
nent yolk plug projecting dorsally and showing practically no recovery 
of the posterior growing region. The head region is relatively small, 
but the ventral suckers are only slightly reduced. The embryo shown 
in 42 is markedly microcephalic, with no trace of the ventral suckers, 
the yolk plug projecting more ventrally and showing a considerable 
recovery of the posterior growing region (tail bud). While the majority 
of embryos from this experiment approximated the type shown in 
figure 42, there were a number similar to the others illustrated in figures 
39 to 41, as well as practically all intermediate stages between the two 
types. These variations in the degree and type of recovery under these 
severe inhibiting conditions represent in all probability simply individual 
differences in susceptibility. Furthermore, the concentration used is 
of such severity that it lies near the border-line between conditions 
where recovery will not take place at all and conditions where it occurs 
readily. Consequently, considerable variation is to be expected (p. 484). 
Figures 43 to 46 illustrate three embryos from experiment IV 22a. 
The treatment was: forty-eight hours in m/10.62 LiCl and subsequently 
eighty-three hours in water. Figures 45 and 46 are lateral and ven- 
tral views, respectively, of the same embryo. All of the embryos are 
microcephalic, ventral suckers partially or completely ‘fused,’ and with 
yolk plugs still protruding. A considerable number of forms with 
spina bifida appear. Differential recovery is evident in a number of 
them (fig. 44), as evidenced by the dorsal convexity and relatively 
large tail buds. 
