MODIFICATION OF DEVELOPMENT IN THE FROG A85 
investigators, it has seemed unnecessary to burden the reader 
with a detailed account of all of the experiments done in this 
laboratory. That the results are consistent and repeatable is 
apparent at once from the literature of the subject. I have 
carried out some two hundred series of experiments, involving 
at least one repetition for each experiment. Those involving 
lithium chloride, potassium cyanide, mercuric chloride, hydro- 
chloric acid, sodium hydrate, and formaldehyde were. repeated 
anywhere from three to six or eight times. The experiments 
described are given usually in protocol form and involve mostly 
agents not hitherto used in experimental teratology (frog). 
Several experiments with LiCl are described in some detail be- 
cause of the attention that, in the past, has been directed to it as 
having a ‘specific’ effect in the production of abnormal forms. 
It should be mentioned that of the four types of modified de- 
velopment recognized here, three, viz., differential inhibition, 
acclimation, and recovery, are more or less the same thing that 
Stockard (21) refers to in Fundulus as ‘developmental arrests,’ 
or, as we would put it, differential developmental arrests. Accli- 
mations and recoveries are of course primarily differential in- 
hibition forms that have, under a change in the experimental 
conditions undergone a remodification that is opposite in direc- 
tion to the previous inhibition. The type characterized here as 
differential accleration is in addition to the one general type of 
modified development recognized by Stockard for Fundulus. 
EXPERIMENTAL DATA 
Experiments with lithium chloride. Eggs unsegmented at the begin- 
ning of the experiment. inthis series the concentrations of LiCl used 
were: m/7 (experiment IV 20); m/8.5 (experiment IV 21), and m/10.62 
(experiment IV 22).° These concentrations in percentages are approxi- 
mately, 0.6, 0.5, and 0.4, respectively. Eggs from a single female, 
one and one-half hours after deposition, were divided into four lots, 
5 ec. of egg mass to each. Three lots were placed, each into a liter of 
the above solutions, the fourth constituting the control. The time at 
which eggs were examined is measured from the time the eggs were 
placed in the solutions. The temperature where the experiments 
were carried on was maintained at 17 + 1°C. 
5 Certain phases of these experiments were discussed in the previous report 
(Bellamy, ’19, pp. 339-340). Through a typographical error, experiment IV 20, 
middle page 339, appears as IV 21. 
