282 T. H. Morgan 
The table shows a number of important details not mentioned 
above. The minimum and maximum number of eggs laid by the 
stem-mother can be approximately estimated from the data. The 
extremes vary between 1 (in No. 20) and 60 (in No. 115). It 
is true that still larger numbers are found in some other cases, 
but in most of these the wingless individuals of the second genera- 
tion were already full sized and may have begun to layeggs. In 
fact in some cases, especially in the last ones given, this is certainly 
true, since large and small eggs were present.° ‘The smallest 
numbers also may not represent the entire output, since many of these 
galls were still small and later would no doubt contain more eggs 
of the stem-mother. Nevertheless since in some of these cases the 
second generation, consisting of a few individuals, contained fully 
grown insects, it is probable that the complete number of eggs had 
been laid. This conclusion is confirmed when we find, as in No. 
106, a dwarf female was present and only two other individuals. 
Another interesting point is also brought out. In No. 165 
there were 17 large individuals (or young ones that would have 
become larger) and 6 dwarfs. This means approximately that 
the first 17 eggs developed into large individuals, and the 18th 
was a dwarf. It follows that there is no fixed number of large 
productive individuals but the conditions determine the result. 
The conclusion 1s of some general importance since 1t shows that 
external conditions may be responsible for producing not a graded 
series of differences, but a sudden change, in other words, a mutation. 
The eggs have therefore a dual capacity, external conditions 
determining which alternative is realized. 
The largest number of large individuals, including wingless and 
°As many as 83 were recorded in another count: (See ante). 
*Several measurements were made of the three kinds of parthenogenetic eggs. These gave the 
relative sizes of the eggs. 
STEM-MOTHER EGGS MALE EGGS FEMALE EGGS 
16 X 9 16 X 9 20 X I0 
I7-X 9 18 X 9 20 X II 
14 X 8 17 X 8 20 X gf 
re X'S 
15 X 8 
