498 A. W. BELLAMY 
quite toxic in concentrations of m/5000 or higher, the toxicity appears 
gradually to grow less, due to the formation of the insoluble oxide. 
Eggs in an eight-cell stage were placed in m/5000 potassium per- 
manganate, and after 48 hours’ exposure a series of stages was present, 
varying from nearly normal yolk plug stages to equatorial gastrula 
stages. The controls at this time were in neural fold stages. After 
72 hours most of the embryos were of the type designated as differen- 
tial recovery forms. The heads are relatively very large and the ven- 
tral suckers and gill plates are prominent. At this time there still 
remained alive a few equatorial gastrulae and several spina bifida forms, 
microcephalic and with the persistent yolk plug situated dorsally. 
Variations of this sort can hardly be avoided in material such as the 
frog egg for reasons already set forth. Moreover, the thickness of the 
gelatinous membranes varies somewhat, especially after the large egg 
masses have been cut apart into smaller masses containing ten or a 
dozen eggs, as was done in all of the experiments. In this particular 
experiment approximately 75 or 80 per cent of the embryos were of the 
differential recovery type, so that on the whole the results are perfectly 
clear-cut and definite. 
Figures 41, 42, which are described on page 486, represent what 
appear to be variations in recovery for which the factors mentioned 
above are, I believe, in part responsible. In addition, the conditions 
under which these embryos were produced were severe enough that 
recovery rarely occurs at all. Consequently, some variation is to be 
expected. But whatever the extent of the variation may be, the signifi- 
cant point is that for the most part, recovery following a previous 
inhibition is differential. Figure 44 illustrates differential recovery 
following a previous treatment with lithium chloride. 
It is not always possible to distinguish between acclimation and 
recovery, especially under conditions like the permanganate experi- 
ment cited above. In this case the strength of the solution is gradually 
changing, due to the reduction of the permanganate (the solution was 
not changed during the course of the experiment). But little or no 
acclimation occurs under the conditions which produced some of the 
embryos. Hence, in this case the results are in all probability a conse- 
quence of the earlier inhibition and later recovery. Many of the em- 
bryos were convex dorsally and the tail buds were relatively large and 
Maen Similar embryos appeared after the following treatment : 
2 days in water (blastopore closed and medullary folds appearing at 
this time), plus 2 days in m/10,000 KNG, plus 2 days in water. The 
differential was even more marked in these embryos (experiment KNC- 
CxaiB): 
Recovery of the embryo, then, is differential in the same sense that 
inhibition is differential. Those regions of the embryo that are nor- 
mally most active, recover soonest when the developing animal is 
removed from the inhibiting conditions. 
